Belarus' opposition supporters protest against President Alexander Lukashenko in downtown Minsk  [AFP]

A group of protesters have staged a demonstration outside Belarus' Palace of the Republic, just hours after the inauguration of long standing leader Alexander Lukashenko.

The president of Belarus had warned on Friday that no dissent would be tolerated as he took the oath of office for a fourth time in a ceremony that was boycotted by European Union ambassadors.

However, the protesters ignored his threats, some of the protesters were arrested by the police.

While holding a copy of the Belarusian constitution, protester Maxim Vinyarsky said he swore "never to recognise Alexander Lukashenko as a legitimate ruler."

"I put my hand on the Constitution, I hold it in my hand and I swear never to recognise him as president but consider him an usurper, illegally holding power in his hands," he said.

Lukashenko was re-elected last month in a vote widely seen as fraudulent and has since cracked down on the opposition, including jailing hundreds of opposition protesters and also seven candidates who ran against him in the 19th December poll.

Lukashenko also closed the office for the Organisation for Security and Cooperation in Europe after its election observers called the vote flawed.

The 56-year-old president has accused Poland and Germany of plotting to overthrow him, claims both countries have rejected.

The EU has threatened to re-impose travel restrictions on Lukashenko and other top officials over the flawed elections and subsequent crackdown if 30 opposition activists, including four presidential candidates, are not released. Lukashenko, who appeared to rule that out on Thursday, ordered his government to prepare harsh retaliatory measures if the sanctions are applied.

The travel ban on Lukashenko and others had been lifted in 2008 as the country, once described by the United States as Europe's last dictatorship, made modest progress on rights issues.

Several EU member states and the EU's Foreign Affairs chief Catherine Ashton also have said they may reinstate the ban when EU foreign ministers meet in Brussels on 31st January.