Moscow slammed Kiev Thursday for violating the ceasefire in eastern Ukraine, accusing it of intensifying its military offensive against rebels.

"It is obvious today that these agreements have been crudely violated by the Ukrainian side," the Russian foreign ministry said.

As a deadline for the controversial delivery of a warship to Russia nears, France faces a grueling dilemma: ditch the deal, lose billions and antagonize Moscow -- or go ahead and attract NATO's wrath.

Until the deadly crisis in Ukraine erupted this year, the 1.2 billion-euro ($1.5-billion) contract to build and sell two mammoth Mistral-class assault ships to the Russian navy had been firmly on track.

Ukraine on Thursday announced passport controls around areas held by pro-Russian separatists in the latest step toward what resembles the breakup of the ex-Soviet republic, as heavy artillery fire erupted in Donetsk.

Ukraine's border guards service said anyone crossing in or out of rebel areas will have to present a passport. Foreigners will "be sent to filtration points to determine the purpose of their visit" and will have "to show a passport or the required visa," a statement said.

Russia has confirmed it will not attend the 2016 Nuclear Security Summit, a gathering championed by President Barack Obama, accusing Washington of seeking to play first fiddle on matters of nuclear safety.

In another sign of the growing chill between the former Cold War rivals, Moscow claimed the organizers wanted to accord special rights to the United States along with South Korea and the Netherlands, which hosted previous summits, while discriminating other participants.

U.S. authorities are investigating a member of Russian President Vladimir Putin's inner circle for money-laundering, The Wall Street Journal reported Wednesday.

In a politically thorny tightening of screws on Putin's billionaire allies, the Justice Department and New York state prosecutors are looking into whether Gennady Timchenko transferred funds linked to allegedly corrupt deals in Russia through the U.S. financial system, the Journal reported citing a number of unnamed people familiar with the case.

U.S. Secretary of State John Kerry on Wednesday warned Russia that sanctions pressure could be intensified over the Ukraine crisis but urged Kiev not to get drawn into "tit-for-tat" measures.

Speaking to reporters in Paris after holding talks with French Foreign Minister Laurent Fabius, Kerry said "the choice is Russia's" as to whether to implement the Minsk agreement that was supposed to bring peace to Ukraine's restive east.

Two teenagers were killed on Wednesday when shelling hit a school sports ground where they were playing football in east Ukraine's rebel-held Donetsk, an AFP journalist and local officials said.

Two corpses lay covered by tarpaulin at the playing field close to the disputed airport in the war-torn city and witnesses said that at least four more people were wounded.

The ceasefire in Ukraine hung by a thread Wednesday after President Petro Poroshenko accused pro-Russian rebels of endangering the peace process and ordered troop reinforcements to eastern cities.

In another sign of how far apart the two sides are drifting, Prime Minister Arseniy Yatsenyuk announced he was cutting the rebel-held Donetsk and Lugansk regions off from central government subsidies, so as not to finance "terrorists."

The leaders of Malaysia and the Netherlands vowed on Wednesday to keep pressing for access to the crash site of Malaysia Airlines flight MH17 and to bring to justice those responsible for downing the plane in Ukraine.

Prime Minister Najib Razak met with his visiting counterpart Mark Rutte in Malaysia to discuss the Dutch-led investigation into the July 17 disaster, which killed 193 citizens of the Netherlands.

Elections held by pro-Russian rebels in eastern Ukraine threaten to close the "window of opportunity" for a peaceful solution to the bloody crisis, EU foreign affairs head Federica Mogherini said Tuesday.

"The main risk I see now is that we close this window of opportunity for internal dialogue and for dialogue with Russia" on implementing a peace plan all sides agreed on in September, Mogherini told a press conference with NATO chief Jens Stoltenberg.