Two blasts in Algeria's capital Algiers have killed at least 23 people and injured 160 - one exploding near the prime minister's office.
The attacks in Algiers are the worst in the capital for years
A caller claiming to represent al-Qaeda in the Maghreb told an Arabic TV channel that his group had carried out the attacks.
There has been no independent verification of the claim.
Prime Minister Abdelaziz Belkhadem, who was unharmed, called the attacks a "cowardly and criminal act".
The official APS agency, quoting the Algerian authorities, said at least 12 people were killed and 118 injured in the attack on the government building and 11 people were killed and 44 injured in the second attack, on a police station in the eastern district of Bab Ezzouar.
'Cowardice and betrayal'
The violence in Algiers comes a day after the authorities in neighbouring Morocco said they had foiled a plot to target foreign and strategic interests by suicide bombers. Three suspects blew themselves up after being pursued by the authorities, and a fourth was shot dead by police. It also follows clashes with militants in Tunisia earlier this year.
Violent attacks have been increasing in Algeria since the main Islamist rebel group, the Salafist Group for Preaching and Combat (GSPC), changed its name to the al-Qaeda Organisation in the Islamic Maghreb in January.
Al-Jazeera TV said this was the group that had claimed responsibility for Wednesday's violence.
BBC Arab Affairs analyst Magdi Abdelhadi says many analysts will link the surge in violence with the ambitions of the Algerian hardline organisation to spread its campaign to neighbouring countries.
The city centre explosion was so loud it could be heard up to 10km (six miles) away, residents said.
Government employees were injured by flying glass and debris, which spread up to 300m (yards) from the site of the blasts.
Ambulances went to the scene and police blocked entry to the prime minister's office, which also houses the offices of the interior minister.
Speaking on Algerian radio, Mr Belkhadem denounced the bombings, which come as the government says it is working towards national reconciliation.
"This is a crime, a cowardly act," Mr Belkhadem said.
Our analyst says the attacks are a serious blow for the Algerian authorities which have for years fought Islamist militants. Despite an amnesty announced two years ago, the violence in Algeria has never completely died down since its height in the mid-1990s.
The latest scenes of blood on the streets of Algiers will revive painful memories of that civil strife that lasted for a decade and left an estimated 150,000 people dead.
Magdi Abdelhadi says the spectre of a resurgent al-Qaeda operating in North Africa, close to Europe's southern border, will send the alarm bells ringing in European capitals. It may also have a devastating impact on the prospect of more open and democratic societies in the region.
He says that like in other Arab states, the authorities have used the threat of terror in the past to curb civil and political freedoms.
I was in a building not very far from the police station where the second bomb exploded. At first we thought that it was an earthquake. Students were confused and crying. Everything came to a standstill. There was no transport and everywhere was blocked. Just last week there were two bomb threats at two universities. Some of the students were in the middle of an exam and had to be evacuated. I really wonder what is next.
Amina Rashid, Bab Ezzouar, Algeria
My husband is visiting his family in Bab Ezzouar. The police station in Bab Ezzouar is located on the edge of a big park where the popular playground faces the front entrance. I'm really happy not to be in Alger. We take the kids to that park everyday when we're there.
Leila , Stockholm, Sweden