Russia's Foreign Minister Sergei Lavrov has warned that protests in Ukraine are "getting out of control".
He described violent clashes between anti-government protesters and police as "scary" and accused EU politicians of stirring up the situation.
Tuesday saw an uneasy standoff on the street of the capital after a second consecutive night of clashes.
Young men threw fireworks and petrol bombs at police guarding the road leading up to the Ukrainian parliament.
Police beat some protesters.
Protesters have been camped out in Kiev since late November, angered by the government's turn to Moscow and its rejection of a planned treaty with the EU.
New anti-protest laws, hastily passed by parliament last week, will come into force on Wednesday.
Mr Lavrov's warning came after Ukrainian President Viktor Yanukovych on Monday said the violence threatened the country's stability.
Warning that the "situation is getting out of control", Mr Lavrov added: "We have information that much of this is being stimulated from abroad," and condemned the violence as a "complete violation of European standards of behaviour".
Clashes continued throughout Monday night, with police using tear gas and stun grenades against several hundred young men who ranged against them. At times, thousands of people cheered from the sidelines.
'Paid thugs'
The violence has been restricted to a small area around Hrushevskyy Street, close to the main protest encampment at Maidan (or Independence Square), with most of the rest of the city functioning normally, say correspondents.
People standing near the fighting reported receiving a text message shortly after midnight on Tuesday, which said: "Dear subscriber, you are registered as a participant in a unsanctioned rally."
Mobile phone operator KievStar denied sending the messages and it is unclear who did.
Meanwhile, peaceful protesters have blamed a little-known far-right group, Right Sector, for carrying out the violence.
Former boxing champion and opposition figure Vitali Klitschko has also accused the government of paying thugs nicknamed "titushki" to delegitimise the protests and create a pretext for the imposition of a state of emergency.
BBC Russian spoke to several suspected "titushki" detained by the opposition activists.
Source: BBC
