One person has reportedly been killed and six others injured as police riots following the re of President Azali Assoumani.
Authorities in Comoros have cut access to the internet in the wake of protests by angry opposition supporters in the capital, Moroni.
Several roads in the capital have been barricaded and an unspecified number of protesters arrested.
A night-time curfew has been imposed to curb the spreading unrest. The electoral commission on Tuesday announced that Mr Assoumani had garnered 63% of the vote in Sunday’s ballot to secure a fourth term as president.
The declaration triggered violent protests after opposition parties termed the results fraud and called for their cancellation.
Buildings in the capital were vandalised, looted and burned, including the home of a minister.
A car at the home of another minister was also burned and a national food depot burnt down during the protests.
Internet services have been severely disrupted and some sites are inaccessible, Global internet monitoring site Netblocks confirms.
WhatsApp calls have been blocked and mobile messages restricted due to very low connection speeds, Comores Infos news website reports.
It says the aim was to prevent demonstrators from communicating and sharing compromising images on social networks.
Government responds to violence
Daoudou Abdallah Mohamed, opposition Orange party official, told AFP news agency that the protests were a “spontaneous uprising against autocratic rule”.
Mr Mohamed said the opposition did not organise the protests but they were “in solidarity” with the protesting youths.
Government spokesperson Houmed Msaidie said the state would not give way to violence, adding: “We know the instigators.”
Mr Assoumani’s poll victory is expected to be confirmed by the Comoros’ Supreme Court at the weekend.