Gabon's opposition leader Jean Ping has told the BBC that 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 Bongo a second seven-year term with 49.8% of the vote to Ping's 48.2% - a margin of 5,594 votes.
But Ping said the election was fraudulent and "everybody knows" he won.
Ping won in six out of nine provinces but disputes the result in Bongo's home province of Haut-Ogooue, where turnout was 99.93% and 95% of votes were for the president.
Turnout in the other provinces was between 45% and 71%, 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".
Ping has called for voting figures from each polling station to be made public.
The US and EU have also called for the results to be published, while UN Secretary-General Ban Ki-moon has urged calm.
The BBC's Charles Stephane Mavoungou reports from Libreville that on Thursday people in the capital have been unable to access the internet, including social media.
The Boulevard Triomphal, home to Gabon's parliament, was covered in burnt-out cars and lined with torched buildings on Thursday, reports the AFP news agency.
It said police used tear gas to prevent crowds from gathering again and arrested people as they emerged from remains of the parliament.