Supporters of Abkhazia presidential candidate Sergei Bagapsh have stormed the president's office in Georgia's breakaway region, say reports.
Electoral officials alleged pressure from Bagapsh supporters
Thousands of demonstrators descended on the headquarters of President Vladislav Ardzinba in Sukhumi on Friday.
They are protesting against a ruling to hold a repeat election after they claim Mr Bagapsh won the vote in October.
His main rival, Raul Khajimba, disputed the result and the election was declared invalid.
Abkhaz Prime Minister Nodar Khashba told Interfax news agency: "The government, parliament and presidential administration buildings have been seized by Bagapsh's supporters.
"All these events can only be described as mass disturbances."
He said he had instructed security officers guarding the buildings not to open fire at the attackers "to avoid irreversible consequences".
For months, Mr Khajimba, a former prime minister, was groomed by Moscow to become the future president of Abkhazia. But official results of the 2 October poll showed he had lost.
He asked for the recount but the result was still the same and Mr Bagapsh remained the winner.
The election was later declared invalid by the Supreme Court and a new vote ordered by the president.
Mr Bagapsh's election team has refused to accept that decision, and he has been preparing for his inauguration.
Mr Bagapsh told the Associated Press news agency: "We were victorious in the election. That means that my inauguration as president will take place on 6 December."
In the beginning of the 1990s, Abkhazia fought a vicious war with Georgia and has since struggled to recover.
It was once Georgia's most prosperous Black Sea province, a place known as the Riviera of the Soviet Union, but today Abkhazia is poor and isolated.