Ukraine’s parliament is to decide whether to bring in martial law as anger over the capture of three of its naval vessels by Russia spilled into the streets overnight.
Protesters gathered outside the Russian embassy in the capital Kiev and an embassy car was set on fire.
The incident in waters off the Crimean Peninsula marks a major escalation of tension between the two countries.
The UN Security Council will hold an emergency meeting as a result.
Each country blames the other for the incident in which two gunboats and a tug were captured and a number of Ukrainian crew members injured.
Later, about 150 people gathered outside the Russian embassy, some throwing flares. At least one car belonging to the embassy was set alight.
“We gathered here today to protest against Russians over their actions today, over shooting of our military,” Oleksiy Ryabov told Reuters news agency.
“We are very angry. We should have severed all diplomatic relations with this country a long time ago.”