Gabon’s opposition leader Jean Ping has told the BBC a presidential guard helicopter bombed his headquarters and killed two people.
A government spokesman said the operation was to root out “criminals” who had set fire to parliament.
Protestors took to the streets on Wednesday claiming fraud after it was announced that President Ali Bongo had been narrowly re-elected.
There has been gunfire in the capital Libreville on Thursday.
The official 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.
But Mr Ping said the election was fraudulent and “everybody knows” he won.
Mr Ping won in six out of nine provinces and disputes the result in one province which show a 99.93% turnout and 95% voted for Ali Bongo.
Just 71% of the electorate voted in the province with the next highest turnout, according to Gabon’s interior ministry.
EU election monitor spokesperson Sarah Crozier told BBC Newsday “it’s not a very common result, that’s for sure”.
Mr Ping 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.