Mr Strache (left) said the far-right were "the winners" of the polls
The leaders of Austria's two far-right parties have hailed the results of snap general elections, which saw their support doubling since the 2006 polls.
The Freedom Party and the Alliance for the Future of Austria took nearly 29% of the vote, preliminary results show.
The Social Democrats won the polls with 30%. But they, and the conservative People's Party, with 26%, suffered their worst results since 1945.
The shape of a possible coalition will now be hard to predict, experts say.
A total of 183 parliamentary seats were up for grabs in Sunday's election.
The early polls were called after the grand coalition between the Social Democrats and the People's Party collapsed this summer amid internal fights and personal feuds.
"Today, we are the winners of election night," Freedom Party leader Heinz-Christian Strache said.
Mr Strache also suggested that he was interested in becoming the next chancellor, according to the Associated Press news agency.
Leader of the Freedom Party Heinz-Christian Strache celebrates its gains
Joerg Haider, the leader of the Alliance for the Future of Austria, told the BBC that both the Social Democrats and the People's Party were now in "a difficult situation", predicting that any coalition talks between them would fail.
"Therefore I think after some talks between these two parties, we will have the opportunity to negotiate the new government."
The Freedom Party had won 18.01% of the vote, Interior Minister Maria Fekter said.
The Alliance for the Future of Austria - which split from Mr Sprache's party in 2005 - had 10.98%.
The rise in support for the far-right parties is the result of protest votes on a variety of issues, the BBC's Bethany Bell in Vienna says.
The resurgent far-right can be attributed to a mixture of anti-European Union sentiment, some anti-immigrant positions and a general sense of discontent with the two traditional centrist parties, our correspondent says.
The far-right showing was even stronger than in 1999, when the Freedom Party won 27% and gained a place in the coalition government with the conservatives.
The nationalists could now re-enter government but only after all other options are exhausted, analysts say.
The most obvious solution would be another grand coalition between the Social Democrats and the People's Party - an option most Austrians oppose, our correspondent says.
16- and 17-year-old voters: 200,000
National Council seats: 183
Social Democrat leader Werner Faymann on Sunday reiterated that he would not be joining forces with either of the two far-right parties.
Wilhelm Molterer, who heads the People's Party, has so far made no public comments on his possible coalition allies.
But referring to Sunday's polls, he said: "This is the worst result in the history of Austria's People's Party."
Final results will not be released until 6 October after absentee and postal ballots, making up about 10% of the votes, are counted.
For the first time in an EU country, 16 and 17-year-olds were able to vote. This bloc represented about 200,000 of the 6.3 million-strong electorate.
I never expected that the two far-right parties could gain so much support. I am 16 years old, which means, I was one of the first-time voters and I am deeply worried about the future of Austria. Among those who are younger than 30 years the FPÖ (Freedom Party) has achieved the most votes - a shocking result! Awful, if you ask me. Tobias Himmelbauer, Steyr, Austria
As a first-time voter I am glad to see the direct impact of young people to democracy. I can understand the fears of a slide to the right wing, but I am definitely sure that a major part of those who voted right wing parties simply voiced their discontent with the disputes between the grand coalition parties. Therefore, there is no reason for fears of a new "Nazi-Austria". Rupert, Austria (Graz)
This is a horrific result but it was obvious that this was going to happen. Here is my attempt to explain this result: Austrians in general are not "right-friendly" at all. It was a vote to show the two major parties (social democrats and the conservatives) that they didn't do a very good job in the past two years. I think Austrians are shocked with the result and some actually don't even feel safe there anymore. It is terrible what bad politicians can do to a great country. Stefan Herovitsch, Soll, Tirol, Austria
Slogans like "Austria for Austrians" and "Our land for our children" have been tolerated by the government during the electoral campaign, showing the deep xenophobic state of Austrian society. At the same time all sectors of Austrian everyday life cannot exist without foreigners, from the cleaning services to the great orchestras. These results are not only a slash in the face of the two big parties. It is an insult for all democratic, peaceful and progressive forces in Austria. But the future is multicultural. Schools are filled with Austrian children whose parents are not Austrian born. I just wonder how voters of FPÖ and BZÖ imagine their country: no-one to work in their factories, no-one to preach in their churches, no tourists, no musicians, no artists, no EU, only 'pure bloods', poor and old inhabitants of an empty country. A pretty odd place. Lawrence K., Vienna, Austria
Unfortunately I could not vote in the elections, as I am a British citizen. The results show that a lot of the young (16 to 18-year-olds) voted FPÖ, due to their ability to get across simple, clear messages. The communication of the Green party was abysmal, the SPÖ and ÖVP were punished for their childish bickering in the last government, so people generally went for the simple solution of the neo-fascists, unfortunately. Now it is up to Mr Faymann and a new ÖVP leader (Mr Pröll probably) to form a coalition that lasts, and not give in to bickering. I would also like to see the Greens in a coalition, as, although they only got 10%, it is up to the democratic centre-left to oppose the far-right. I am appalled by this result - Austria should be ashamed of itself. Rod Pritchard-Smith, Vienna
I suppose there will be another election by next spring because with this results there is no constant majority to build a cabinet. The far right will hopefully not be asked to join the government. Where such a step can lead to we have seen in the past. And continuing a grand coalition is definitely not the best idea - after having caused the early election this is not exactly what Austrians want to. If they do so, the question is: what are elections for? Ask the public what they want and then reject their vote and carry on? I am not sure if this is the best way. It seems to become an Austrian hobby - going regularly to elections. Klaus, Vienna
I'm feeling ashamed of being Austrian. Sunflowers1979, vienna
I feel ashamed living in this country! Right extremism is unfortunately not history in Austria, it's the reality. Social Democrats and People's Party failed with their programmes to keep the electorate on their side. Moreover, the electorate is obviously not only desperate, but too dumb to resist the propaganda of the right wing. More education for Austria! Benedikt Weigand, Vienna, Austria
It is the third time I am voting. I got citizenship 10 years ago and in all these years I followed with high interest the political development in Austria. As for the last election, I would not say that the win of the two right parties (FPÖ and BZÖ) are only results of protest again SPÖ and ÖVP. I believe this is a kind of natural development in all the democratic countries. The frustration of the population facing tough economical challenges, missing of a clear programme for the future of the big coalition, internal political changes inside SPÖ and ÖVP, the need for a change as well as a new generation of voters with total different view on the globalisation and EU policy are some of the natural factors of this results. Adrian Haxhiaj, Vienna
I am from England, and have lived in Austria for just over a year, and am disappointed and angry that people made their "protest vote" by voting for the far right, I am a little confused by this way of protesting, and giving their democratic right to vote for some populist and racist parties. There are better ways to protest. Alfred Frodden, Austria
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