Ukraine’s parliament is to decide whether to bring in martial law, after Sunday’s capture of three of its naval vessels and 23 crew members by Russia.
The three ships were sailing off the coast of Crimea, which was annexed by Russia in 2014, when they were seized.
Russia opened fire, before its special forces stormed the vessels. Between three and six Ukrainians were injured.
Ukraine said it was a Russian “act of aggression”. Moscow said the ships had illegally entered its waters.
On Monday, Ukrainian President Petro Poroshenko said he was proposing that parliament back a 30-day martial law - half the length of that recommended by Ukraine’s security and defence council a day earlier.
In a televised address, Mr Poroshenko said he did not want martial law to affect presidential elections set for 31 March 2019. If backed by MPs, martial law would enter into force at 09:00 local time (07:00 GMT) on 28 November.
Sunday’s clash between Russian and Ukrainian vessels marks a major escalation of tension between the two countries.
This is the first time the two militaries have come into open conflict in recent years, although Ukrainian forces have been fighting Russian-backed separatists and Russia volunteers in the east of the country.