Gabonese security forces have stormed the headquarters of the defeated presidential candidate, Jean Ping, as unrest continues after Saturday's disputed election.
A government spokesman said the operation in the capital, Libreville, was aimed at rooting out "criminals".
Mr Ping said two people had been killed in the assault on his headquarters.
His supporters have staged protests after official results gave President Ali Bongo a narrow victory.
They have accused the government of stealing the election.
The government has said security operations have been targeting "armed criminals" who had earlier set the parliament on fire.
Mr Ping, a former Gabonese foreign minister and African Union Commission chairman, denounced the raid on his headquarters.
"They attacked around 01:00 (00:00 GMT). It is the republican guard," he said. "They were bombarding with helicopters and then they attacked on the ground."
Mr Ping, who was not in the building himself, has called for international assistance to protect the population.
The election result, announced on Wednesday afternoon, gave Mr Bongo a second seven-year term with 49.8% of the vote to Mr Ping's 48.2 %, a margin of 5,594 votes.
Mr Ping said the election was fraudulent and "everybody knows" he won.
Protesters took to the streets shortly after the announcement. They set fire to the parliament building and clashed with riot police.
Mr Ping's camp has said figures from the president's stronghold showed a 99% turnout. He has called for voting figures from each polling station to made public.
The US and EU have also called for the results to be made public while UN Secretary-General Ban Ki-moon has urged calm.
Mr Bongo took office in 2009 after an election marred by violence, succeeding his father Omar Bongo who had come to power in 1967.
Mr Ping had been a close ally of Omar Bongo, serving him in ministerial roles and having two children with his daughter, Pascaline, a former Gabonese foreign minister herself.