The headquarters of three opposition parties in the Democratic Republic of Congo have been torched in the capital and two charred bodies have been found at one on of them, a BBC reporter says.
The attacks followed Monday's deadly clashes between police and opposition supporters demanding that President Joseph Kabila step down by December.
The office of the main opposition UPDS was among those set ablaze in Kinshasa.
It has warned Mr Kabila that it will be "treasonous" to delay elections.
The polls are due in November, but the opposition fears that the president wants to postpone them in a bid to cling to power.
He has not yet commented on his plans.
The constitution bars Mr Kabila, who took power in 2001 following the assassination of his father Laurent Kabila, from running for office again in a country that has never had a smooth transfer of power since independence more than 55 years ago.
At least 17 people were killed in Monday's clashes, including three police officers who were burnt alive, said Interior Minister Evariste Boshab.
The opposition put the number of dead at 50, with one witness saying police fired live ammunition into the crowd.
The BBC French service's Poly Muzalia in Kinshasa says it is unclear who was behind the subsequent arson attacks on the headquarters of the three parties.
The two burnt bodies were found at the headquarters of the the Union for Democracy and Social Progress (UPDS), led by veteran opposition leader Etienne Tshisekedi, our reporter says.
Flames were dying down at the headquarters of the Forces of Union and Solidarity (Fonus) when he visited it on Tuesday morning, after it was torched overnight.
The headquarters of the Lumumbist Progressive Movement (MLP) in the north of Kinshasa had also been torched.
The electoral commission was meant to announce a date for presidential elections on Monday, but has said it will not be possible to hold them in November.
A government-backed effort to work out a solution to the political crisis, called a "national dialogue", has been boycotted by most opposition parties.
Mr Kabila's second term is due to expire on 20 December.
Last year at least 12 people died in similar protests.