President Vladimir Putin insisted Wednesday that Russian forces had the right to seize three Ukrainian ships at the weekend, as Kiev lashed out at Moscow for failing to release its sailors.

In his first extensive remarks since the confrontation at sea on Sunday, Putin said it had been orchestrated by Kiev as a "provocation".

He said the Ukrainian ships had entered Russian territorial waters and refused to respond to requests to stop from Russian patrol boats.

"What were they (Russian forces) supposed to do?" Putin said when asked about the incident at an international investment forum in Moscow.

"They were fulfilling their military duty. They were fulfilling their lawful functions in protecting Russia's borders. They would do the same in your country."

AAP

Moscow and Kiev have traded angry accusations since Russian navy vessels fired on, boarded and captured the three Ukrainian ships off the coast of Crimea.

After warning of the threat of "full-scale war", Ukrainian President Petro Poroshenko on Wednesday signed an act imposing martial law for 30 days in regions bordering Russia, the Black Sea and the Sea of Azov.

Western governments have rallied behind Kiev, accusing Russia of illegally blocking access to the Sea of Azov, used by both countries, and of using force without justification.

US President Donald Trump on Tuesday threatened to cancel planned talks with Putin at this week's G20 summit in Buenos Aires over the incident.

0:00 Putin say she hopes to meet with Trump at G20 Summit. 00:00 / 00:00 Share Share on Twitter

Share on Facebook

'Bring our boys home'

The Kremlin said it expected the meeting to take place and played down the threat, with Putin's foreign policy advisor Yuri Ushakov saying: "The meeting is equally needed by both sides."

The Ukrainian vessels - a tug and two gunboats - were trying to pass through the Kerch Strait from the Black Sea to the Sea of Azov, but were refused access and chased into international waters by 10 Russian vessels.

Kiev has demanded the return of its ships and the release of 24 sailors taken prisoner during the confrontation.

EPA

The sailors have been put before a court in Simferopol, the main city in Russian-annexed Crimea, and ordered to be held in pre-trial detention for two months.

Detention orders were made against 15 of them on Tuesday, including three still in hospital, and nine more on Wednesday.

"We condemn this demonstration of barbarism and are multiplying our efforts to bring our boys home," Ukrainian Prime Minister Volodymyr Groysman said on Twitter after the court rulings.

Ukraine's foreign ministry sent Moscow a diplomatic note in protest at the "illegal" detentions.

Sunday's incident was the first direct confrontation between Ukraine and Russia in the long-running conflict pitting Kiev against Moscow and Russian-backed separatists in the country's east.

It has raised fears of a wider escalation - in a conflict that has killed more than 10,000 people since 2014 - and prompted international calls for restraint.

New S-400s deployed to Crimea

Russian military officials said Wednesday that Moscow would soon deploy more of its advanced S-400 air defence systems in Crimea, which Russia annexed from Ukraine in 2014.

One more of the systems would be joining three others already deployed in Crimea, they said.

The Ukrainian parliament on Monday voted in favour of Poroshenko's request for martial law, which gives authorities the power to mobilise citizens with military experience, regulate the media and restrict public rallies in affected areas.

It was unclear how it would be applied in the border areas and Poroshenko has suggested it is meant essentially as a preventative measure.

The European Union, Britain, Canada, France, Germany and others have expressed support for Kiev, in statements pro-Kremlin newspaper Izvestia denounced as "predictably anti-Russian".

President Poroshenko does not stand a chance in the current situation and may not even make it into the runoff. This provocation in the Kerch Strait may have been engineered for pushing through specific political decisions that would benefit the incumbent president — Dmitry Medvedev (@MedvedevRussiaE) November 28, 2018

Russian Foreign Minister Sergei Lavrov shifted the blame to the West, accusing the United States and Europe of encouraging Ukraine.

"I think it reflects Washington's tendency to indulge any and all action taken by the Kiev regime, even inciting them to provocative actions," Lavrov told reporters in Geneva.

Moscow has suggested that Kiev provoked the incident to boost support for Poroshenko, who is facing a tough re-election battle in a presidential vote set for next March.