Greece's new Prime Minister Alexis Tsipras distanced himself Tuesday from a threat by EU leaders to impose further sanctions on Russia over the war in Ukraine, saying Athens was not consulted about the warning.

In a statement two days after his radical left Syriza party won Greece's general election, Tsipras accused EU leaders of failing to consult his government on a joint declaration Tuesday accusing Russia of "growing support" to separatists in Ukraine's east.

NATO allies must stay the course in Ukraine, the top U.S. diplomat for Europe insisted Tuesday, calling for alliance command and control centers to be set up quickly in Kiev's neighbors.

"We have to keep our security commitments to each other," said Assistant Secretary Victoria Nuland said, adding that all NATO allies must contribute to the new "spearhead force which will allow us to speed forces to troubled spots."

About 1,100 children are living rough in underground shelters in Ukraine's rebel-held eastern city of Donetsk, the U.N. children's agency said Tuesday.

"We were able to assess 12 bomb shelters where there are adults and parents with the children," UNICEF's representative in Ukraine Giovanna Barberis said.

An official of the Russian Central Bank in the country's Far East went on a rampage at work Tuesday killing three colleagues and then shooting himself, investigators said.

A deputy head of the central bank's regional branch in the city of Blagoveshchensk mowed down two women and one man at the bank's offices before committing suicide, a spokesman for the region's investigative committee Alexei Lubinsky told Interfax news agency.

Moscow on Tuesday blasted the United States over the arrest of an alleged Russian spy, condemning the move as a "provocation" that would further damage already tattered ties.

"The U.S. has decided to launch the latest stage of its anti-Russian campaign," the foreign ministry said in a statement, accusing Washington of "stoking spy mania". 

An inquiry into the radiation poisoning of a former Russian spy opened Tuesday with claims that there may have been an earlier assassination bid in the most sensational tale of espionage since the Cold War.

Alexander Litvinenko was killed -- apparently via a cup of green tea laced with hard-to-detect polonium-210 -- in an upmarket London hotel in 2006.

European Union leaders on Tuesday threatened new sanctions against Russia over a bloody offensive by pro-Kremlin Ukrainian rebels, backing, the latest bid to pressure a defiant President Vladimir Putin.

The decision came a day after Standard and Poor's downgraded Russia's foreign currency rating to junk because of its eroding economic health, weakened by a wave of Western financial restrictions last year and the plunging price of its oil exports.

Fighting in east Ukraine over the last 24 hours has killed at least nine soldiers and wounded 29, the military said Tuesday, as rebels fought to secure more territory in the war zone.

A rocket attack on the Ukrainian city of Mariupol that killed 30 people at the weekend deliberately targeted civilians and the perpetrators must be brought to justice, a senior U.N. official said Monday.

U.N. Under Secretary-General Jeffrey Feltman told an emergency Security Council meeting that a crater analysis by European monitors showed the rockets were fired from territory controlled by pro-Moscow rebels.

Masked Russian riot police on Monday raided the office of a television channel serving Crimean Tatars, a minority ethnic group in Crimea that opposed Moscow's seizure of the peninsula from Ukraine last year.

In a move the Organization for Security and Cooperation slammed as "intrusion" against the freedom of the media, dozens of armed masked men searched the headquarters of the ATR channel in the regional center Simferopol, seizing servers and other equipments.