The European Union will add to its sanctions list 15 Ukrainian and Russian individuals and 18 entities over their role in the Ukraine crisis, an EU source said Thursday.

The source said the 18 entities will be made up of nine companies and nine institutions, such as the local authorities set up by pro-Russian rebels that have proclaimed independence in eastern Ukraine.

Ukraine's Prime Minister Arseniy Yatsenyuk on Thursday resigned in a shock move in protest at the disbanding of the ruling parliamentary coalition, plunging the strife-torn nation into political uncertainty.

"I announce my resignation in connection with the dissolution of the parliamentary coalition and the blocking of government initiatives," a furious Yatsenyuk told parliament.

Fighting between Ukrainian troops and rebels raged Thursday near the crash site of Malaysian flight MH17, as experts in Britain begin analyzing crucial data from the downed airliner's black boxes.

A Dutch team leading the probe into the downing of MH17 was stuck in Kiev, unable to join a handful of international investigators at the site, after two warplanes were shot down Wednesday just 45 kilometers from the impact scene in insurgent-held territory.

A senior Russian official called Thursday on the United States to prove its claims that the Malaysian passenger airliner shot down last week was hit by a missile fired from rebel-held territory in Ukraine.

"They've said U.S. intelligence has technical data and satellite photos which show that the missile was launched from rebel-held territory. The question is where is this data", Deputy Defense Minister Anatoly Antonov said in an interview with Russia-24 television.

Monitors from the European security body OSCE and Malaysian inspectors on Wednesday found parts of the fuselage of the downed Malaysian flight MH17 with "significant puncture marks", the OSCE said.

"Some of the materials we saw and have photographed, feature significant puncture marks to the fuselage, almost a piercing mark," said Michael Bociurkiw, a spokesman for the Organization for Security and Cooperation in Europe's special mission to Ukraine.

A British journalist reporting for a Russian television channel from conflict-torn eastern Ukraine went missing on Wednesday, with Moscow alleging he and another journalist were captured by Kiev's troops.

Graham Phillips, a British national who works as a stringer for state-owned channel RT (formerly Russia Today), went to cover intense fighting around Donetsk airport Tuesday, but RT has had no contact with him since the early hours of Wednesday, it said.

The International Committee of the Red Cross said Wednesday that it considered Ukraine to be in a state of civil war, urging both sides to respect the laws of conflict as civilians bear the brunt.

The formal classification means participants in the fighting between government forces and pro-Russian separatists in the east could eventually be prosecuted for war crimes in international courts.

Rolling hills, sleepy villages and the crackle of gunfire: the area where two Ukrainian fighter jets were downed on Wednesday is a surreal warzone near the flight MH17 crash site.

While OSCE monitors examined the abandoned debris from the Malaysia Airlines plane, the fighting raged some 45 kilometers (25 miles) to the south near Savur Mogila -- an ancient holy site and World War II monument.

Ukraine's western-backed government said Wednesday that it was preparing to slap sanctions on Russia for backing pro-Moscow separatists in the ex-Soviet state.

Ukrainian Prime Minister Arseniy Yatsenyuk said a special committee had been set up to draw up a raft of economic sanctions against any Russian individuals, officials or companies accused of supporting rebels battling government troops in the east of the country.

The black boxes from the doomed Malaysia Airlines flight MH17 that came down in eastern Ukraine have arrived in Britain for expert analysis, the government said Wednesday.

The recorders have been delivered to the Air Accidents Investigation Branch headquarters in Farnborough, southwest of London.