German Chancellor Angela Merkel has spoken out against oppression in Zimbabwe, at a meeting of European and African leaders being held in Portugal.
Mr Mugabe's attendance has overshadowed the summit
She condemned the policies of President Robert Mugabe as "damaging the image of new Africa", sources inside the closed session in Lisbon said.
With Mr Mugabe in the audience, she said she stood with Zimbabwe's people.
Earlier, Portuguese PM Jose Socrates described the gathering - the first for seven years - as a "summit of equals".
However, Mr Socrates, who is hosting the meeting of nearly 70 EU and African leaders, said there would be no shying away from thorny issues such as human rights.
Other key topics include trade, immigration, the environment, and peace and security.
"This summit is a summit of equals," he said. "We are equal in our human dignity... but also equal in terms of political responsibility," he said in an opening speech.
He acknowledged that Zimbabwe was a sticking point, but said dialogue would bring results.
Previous efforts to hold EU-African summits have collapsed over the question of Mr Mugabe's attendance.
Although Mr Mugabe is banned from the EU, African leaders demanded he be invited to attend. UK Prime Minister Gordon Brown has boycotted the meeting in protest.
No shying away
Mrs Merkel has been tasked with expressing the EU's concerns about the situation in Zimbabwe, where Mr Mugabe is accused of economic mismanagement, failure to curb corruption and contempt for democracy.
"The situation in Zimbabwe concerns us all, in Europe as in Africa," she said. "We don't have the right to look away when human rights are trampled on."
There is a growing belief that Europe-Africa relations are changing
The EU Commission President Jose Manuel Barroso also criticised the way President Mugabe was treating the people of Zimbabwe.
"Frankly we hope that those who have fought for the independence and freedom of their countries now can also accept the freedom for their own citizens," he said.
Mr Mugabe, who is still regarded by many African leaders as the heroic liberator of Zimbabwe, has not yet responded publicly to the remarks.
Ghanaian President John Kufuor, who is also president of the African Union, said it was time to shake off the colonial past.
"For almost 500 years, the relationship between our two continents had not been a happy one. It is to correct this historic injustice and inhumanity that this new relationship between Africa and the European Union is now necessary," he said.
Meanwhile, French President Nicolas Sarkozy met his Rwandan counterpart to "start to normalise" ties, which were severed last year in a row over a French inquiry into events that led to the 1994 Rwandan genocide.
"We want to turn the page, we want to look to the future," said Mr Sarkozy following talks with President Paul Kagame.
The BBC's Mark Doyle in Lisbon says there is an emerging realisation in Europe that its relationship with Africa is changing.
Poverty and issues around development aid are still dominant, but at the same time many countries in Africa are now democracies with growing economies and growing self-confidence, our correspondent says.
African trade with China is forcing Europe to take Africa more seriously and not just as a collection of former colonial possessions, he adds.
The EU is hoping to draw up a number of new Economic Partnership Agreements with former African colonies and regional blocs. The World Trade Organization wants the current preferential trade deals to expire at the end of the year.
African representatives are concerned that the new agreements are unbalanced and that their countries will not be able to compete with subsidised European goods.
Some states, though, in East Africa, have already signed up to the new deals.
European countries are mindful of protecting their position in Africa amid rising competition from China, correspondents say.