The Latest: Ukrainian president demands release of sailors

The Latest on tensions between Russia and Ukraine (all times local):

12:50 p.m.

Ukraine's president is demanding that Russia immediately release Ukrainian sailors and ships seized in a standoff in the Black Sea.

Petro Poroshenko said at a meeting of Ukraine's national security council Monday that "we demand that they are urgently turned over to the Ukrainian side" and called for a "de-escalation" of the crisis around Crimea.

Later Monday, the Ukrainian parliament is set to consider a presidential request for the introduction of martial law.

Ukraine's navy said six Ukrainian seamen were wounded when Russian coast guards opened fire on three Ukrainian ships near the Kerch Strait and then seized them late Sunday. The two nations traded blame over the incident. It aggravated tensions that have soared since Russia annexed Ukraine's Crimean Peninsula in 2014 and backed a separatist insurgency in eastern Ukraine.

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11:55 a.m.

NATO is calling on Russia and Ukraine to show restraint after the Russian coastguard fired on Ukrainian navy vessels, wounding six seamen.

Ukraine says the ships were respecting international maritime rules as they headed to the Sea of Azov. Russia says they failed to obtain permission to pass through the Kerch Strait separating Crimea from the Russian mainland. Tensions between NATO and Russia have escalated since 2014 after Russia annexed Ukraine's Crimean Peninsula.

NATO spokeswoman Oana Lungescu said "we call for restraint and de-escalation."

She said NATO supports Ukraine's "navigational rights in its territorial waters" and calls on Russia "to ensure unhindered access to Ukrainian ports in the Azov Sea, in accordance with international law."

NATO headquarters declined to say Monday whether its ambassadors would meet to discuss the incident, but the alliance is in contact with Ukrainian authorities.

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10:50 a.m.

A senior German official is calling on Russia and Ukraine to de-escalate tensions after Russian coast guard ships fired on Ukrainian navy vessels.

Michael Roth, a deputy foreign minister, told Deutschlandfunk radio Monday that the matter is "very dangerous — the last thing we need is a further escalation in relations between Russia and Ukraine."

Roth said he didn't have any information of his own on the incident "but it is clear that Russia, in accordance with international law, must ensure unhindered access to Ukrainian harbors in the Sea of Azov." He added that "both sides must now de-escalate" and avoid a spiral of tensions that "could ultimately lead to terrible consequences."

Moscow and Kiev are trading blame over the incident that further escalated tensions that have soared since Russia annexed Ukraine's Crimean Peninsula in 2014.

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10:20 a.m.

The Ukrainian parliament is set to consider a presidential request for the introduction of martial law in Ukraine following an incident in which Russian coast guard ships fired on Ukrainian navy vessels.

Ukraine's navy said six Ukrainian seamen were wounded when Russian coast guards opened fire on three Ukrainian ships near the Kerch Strait and then seized them late Sunday.

The two nations traded blame over the incident that further escalated tensions that have soared since Russia annexed Ukraine's Crimean Peninsula in 2014 and backed a separatist insurgency in eastern Ukraine.

Ukraine said its vessels were heading to the Sea of Azov in line with international maritime rules, while Russia charged that they had failed to obtain permission to pass through the narrow Kerch Strait separating Crimea from the Russian mainland.