The European Union will next month consider further sanctions against Russia over the latest flare-up in the Ukraine conflict, the foreign minister of Austria, which holds the rotating EU presidency, said.

“On the issue of further sanctions, time will tell — we have a summit in December,” Karin Kneissl told reporters after Berlin talks with her German counterpart Heiko Maas.

“Everything depends on the accounts of events and the actions of both sides. But it will need to be reviewed.”

Ms Kneissl said it was “one side’s account versus the other’s” in the latest tensions, in which Kiev declared martial law in response to Moscow’s seizure of three of its navy vessels.

The facts would need to be studied before conclusions could be drawn, she said. Mr Maas said the latest escalation showed “that the annexation of Crimea... is also a problem for the security of us all in Europe”.

He repeated Berlin’s call for Russia to release the seized ships and sailors and added that “both sides must now do their part for de-escalation”.

It comes as UN chief Antonio Guterres said Ukraine and Russia must exercise “maximum restraint” and aim for a quick reduction in tensions after a naval confrontation sparked the most dangerous crisis in years between the neighbours.

His call came as Russian President Vladimir Putin warned Ukraine against any “reckless acts” after Kiev declared martial law in response to Moscow’s seizure of three of its navy vessels.

A statement from the UN secretary-general urged both sides “to take steps without delay to contain this incident and reduce tensions through all available peaceful means in accordance with the Charter of the United Nations.”

Mr Guterres underscored “the need to fully respect the rights and obligations of all concerned parties” under international law and said “the sovereignty and territorial integrity of Ukraine, within its internationally recognised borders... must also be fully respected.”

Ukraine’s Western allies have accused Russia of using force without justification in the naval confrontation, while Kiev urged its partners to impose further sanctions on Moscow.