Twitter is complaining that its messaging service in Belarus is being blocked and throttled.
In that Eastern European country, it is uneasy after sole ruler Lukashenko won the presidential elections again on Sunday.
The opposition and Western observers assume that the results have been tampered with.
Twitter considers the measures against the service in Belarus as a response to protests from people contesting the election results.
The American company calls the shutdown of the internet extremely harmful. It violates fundamental human rights and the principles of an open internet.
Meanwhile, reports of new clashes between protesters and police in the Belarusian capital Minsk are coming.
Protesters would be arrested again. There were already massive demonstrations on Sunday evening, which were partially suppressed by force.