EU leaders will hold an emergency video talks on Wednesday to discuss the crisis in Belarus, where protests are swelling against the disputed re-election of President Alexander Lukashenko.
The summit was called by EU Council President Charles Michel after Moscow said it was ready to provide military help to its ally Lukashenko, who has ruled Belarus for 26 years.
Tens of thousands of people have taken to the streets to condemn Lukashenko's election win and a subsequent violent crackdown on protesters by riot police.
"The people of Belarus have the right to decide on their future and freely elect their leader," Michel tweeted, saying Wednesday's virtual summit would begin at 12:00 pm (1000 GMT).
READ MORE
Belarusian Tsikhanouskaya says she is ready to lead nation
US helicopter attacks Syrian army checkpoint
Thousands of S.Korea church members quarantined over virus
"Violence against protesters is unacceptable and cannot be allowed."
A European source said Michel decided to call the summit in view of the spike in tensions over the weekend.
Lukashenko claimed victory in the August 9 election with 80 percent of the vote, despite wide opposition to his rule.
The crackdown by security forces has seen more than 6,700 people arrested, hundreds wounded and two people killed.
EU foreign ministers on Friday agreed to draw up a list of targets in Belarus for a new round of sanctions in response to the crackdown and on Monday Germany, which currently holds the EU's rotating presidency, said it was ready to back even tougher measures.
Agence France-Presse