Brussels - EU leaders have agreed to again prolong economic sanctions on Russia for its role in eastern Ukraine and Crimea, calling for the "immediate release" of Ukrainian seamen captured in a recent naval stand-off between Moscow and Kiev.

Sanctions run until mid-2019

During a summit in Brussels on Thursday, EU leaders did not agree to impose any additional sanctions on Moscow over the events last month in waters off the Crimean peninsula.

"Decision: EU unanimously prolongs economic sanctions against Russia given zero progress in implementation of Minsk agreements," Tusk wrote on Twitter, referring to a peace deal agreed between Moscow and Kiev.

The sanctions were first adopted in July 2014 in light of Russia's annexation of Ukraine's Crimean peninsula and its support for separatists in the country's east.

The EU has tied easing the sanctions to progress on the Minsk peace agreement, which calls for an unconditional ceasefire and for both sides to pull back heavy weapons from the front line in eastern Ukraine.

The sanctions, which are now expected to run until mid-2019, target Russia's financial, energy and defence industries, impeding banks' access to EU markets and limiting certain EU imports.

EU: Realease detained Ukrainian seamen

Tensions flared between Moscow and Kiev on November 25, when Russia's coastguard opened fire and captured Ukrainian naval vessels and 24 crew members in the Kerch Strait, which links the Black Sea and the Sea of Azov.

The EU leaders requested "the immediate release of all detained Ukrainian seamen as well as the return of the seized vessels and free passage of all ships through the Kerch Straits," according to a joint statement issued after their talks.

They expressed their "utmost concern" regarding the escalation, as well as "Russia's violations of international law."

"There is no justification for the use of military force by Russia," the statement notes. It reconfirms the EU's commitment to Ukraine's sovereignty, territorial integrity and independence as well as its non-recognition of the annexation of Crimea.

The bloc says that it stands ready to take measures to strengthen its support, including for the affected regions in Ukraine.

EU member states disagree on whether to impose further sanctions over the latest events, with countries such as Germany arguing that the move could harm attempts to negotiate a solution to the crisis.

Italy, Hungary and Austria are among the nations more opposed to further sanctions, while Lithuania is one of the countries that favours a tougher approach.