German Foreign Minister Heiko Maas on Monday called a Russian blockade of access to the Sea of Azov "unacceptable" and urged an easing of tensions with Ukraine following a weekend flare-up.
"The developments are troubling," he tweeted.
"A Russian blockade of the passage to the Sea of Azov is unacceptable. It is important that the blockade be lifted. We call on both sides to deescalate."
Tensions have been building over the Kerch Strait, where Russia has built a new bridge that gives it a land connection to Crimea, which Moscow annexed in 2014.
On Sunday, Russia boarded and seized three Ukrainian ships in the strait off Crimea, accusing them of illegally entering Russian waters in the Sea of Azov.
Ukraine has demanded the release of its sailors and more sanctions against Moscow.
German government spokesman Steffen Seibert said later that Berlin was following the reports with "great concern" and called for "restraint" to prevent further escalation.
"We will closely monitor developments," he told reporters, adding that the German government was in contact with Kiev and Moscow.
"As you know the German government supports the sovereignty and the territorial integrity of Ukraine, which includes the Kerch Strait -- free access to the Sea of Azov must be ensured."
Seibert called the building of the bridge over the Kerch Strait a "violation of international law because Ukraine was not included" and urged Russia to release Ukraine's ships and sailors.
He said the use of military force by Russia was "unjustified based on the facts we have seen to date" and called "both sides to quickly resume dialogue".
The confrontation at sea has raised fears of a wider military escalation and the UN Security Council was to hold an emergency session later Monday to consider a response.
Berlin on Tuesday was hosting a previously scheduled meeting of high-ranking diplomats from Russia, Ukraine, France and Germany known as the Normandy format.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)