German Chancellor Angela Merkel warned Russia Wednesday of new sanctions if the Ukraine ceasefire accord is not fully implemented, insisting that Kiev be allowed to regain full control of its eastern border.

"One thing is absolutely clear, if the Minsk ceasefire accord does not work then (EU) member states and the European Commission are quite prepared to move to new sanctions," Merkel said.

Ukraine's President Petro Poroshenko said Wednesday he has sent a letter to Russia's Vladimir Putin asking him to free jailed pilot Nadiya Savchenko, who has been on a hunger strike for nearly three months.

"I have sent a letter to President Putin with an appeal for immediate freedom for Nadiya Savchenko, including for medical reasons," Poroshenko said in a press conference after meeting Italian premier Matteo Renzi.

Russian President Vladimir Putin on Wednesday described the killing of opposition politician Boris Nemtsov as a tragedy that had brought disgrace on Russia, and warned against a rise in "extremist crime".

"We must pay the greatest attention to crimes that prompt a major reaction, including those that are politically charged," he told interior ministry officials at a televised meeting.

Foreign Minister Jebran Bassil held talks on Wednesday with his Russian counterpart Sergei Lavrov on the latest developments in Lebanon and the region.

The Russian official stressed during the talks his country's support for Lebanon and its “opposition to meddling in its internal affairs.”

Kremlin opponent Boris Nemtsov's blood was barely dry on the Moscow sidewalk before powerful Russians came up with a startlingly clear conclusion: that the West was to blame.

The West stands accused of an increasing number of outrages in President Vladimir Putin's Russia.

One plane was diverted and another delayed to avoid two Russian bombers that flew through Irish-controlled airspace without warning in February, the Irish Aviation Authority (IAA) said on Tuesday.

The disruption is believed to have occurred during the same February 18 incident in which British RAF Typhoon fighters were scrambled to escort two Russian bear bombers identified flying close to British airspace.

A Ukrainian airforce pilot who has been on hunger strike in a Russian jail for 81 days will be transferred to a civilian hospital if her health deteriorates, the prison service said Tuesday.

The statement by Russia's prison service raised the possibility of Nadia Savchenko, who is also a member of the Ukraine parliament, being transferred from the hospital of a Moscow prison where she has been held for nearly nine months.

Leaders of France, Germany and Russia have agreed with Ukraine on the dispatch of OSCE monitors to 10 flashpoint sites on the country's eastern frontline to shore up a shaky truce, Ukraine said Tuesday.

In a readout of a four-way telephone conversation published by the Ukrainian presidency, President Petro Poroshenko, German Chancellor Angela Merkel, French President Francois Hollande, and Russian President Vladimir Putin "supported Ukraine's suggestion to put monitors to all locations of ceasefire violations."

An ethnic Armenian soldier from the separatist Nagorny Karabakh region was killed Tuesday by Azerbaijani troops in a fresh clash along the breakaway region's frontier, the rebel authorities said.

"Serviceman Arsen Karapetyan, 20, was mortally wounded when Azerbaijani forces violated the ceasefire at the Karabakh frontline," Karabakh's defence ministry said in a statement.

Thousands of mourners turned out Tuesday to pay a last homage to slain Russian opposition leader Boris Nemtsov, gunned down near the Kremlin in the most stunning assassination of Vladimir Putin's rule.

Crowds thronged the Russian capital to mourn the 55-year-old former deputy prime minister, a longtime Putin critic and anti-corruption crusader who was laid to rest at a Moscow cemetery.