Prime Minister Najib Razak's step-grandmother was on board the Malaysia Airlines passenger jet that crashed in violence-wracked Ukraine, the country's defense minister confirmed Saturday.

Hishammuddin Hussein, a cousin of Najib's, said 83-year-old Sri Siti Amirah was "on the flight". Siti Amirah was also Hishammuddin's step-grandmother.

Dutch Prime Minister Mark Rutte on Friday vowed "not to rest" in tracking down those responsible for downing Malaysia Airlines flight MH17 if it emerges it was attacked, as Malaysia's premier demanded that the possible perpetrators be brought to justice.

The Netherlands has dispatched Foreign Minister Frans Timmermans and a team of forensic experts to Ukraine to probe the disaster, in which 189 Dutch citizens died.

An initial review of U.S. intelligence suggests pro-Russian separatists likely shot down a Malaysian airliner over Ukraine, but Washington is still examining the evidence, a U.S. official said Friday.

"There are indications (the separatists downed the plane) but there's no final conclusion," the U.S. official, who spoke on condition of anonymity, told Agence France-Presse.

British Prime Minister David Cameron said Friday that if it is confirmed a Malaysian airliner was shot down over Ukraine, those responsible "must be brought to account."

Malaysia Airlines flight MH17 was flying from Amsterdam to Kuala Lumpur when it crashed on Thursday, killing all 298 people on board including nine Britons.

Glen Thomas, a spokesman for the World Health Organisation, was among the 298 people killed in the crash in eastern Ukraine of a Malaysia Airlines jet, the U.N. agency said Friday.

Thomas was headed to Melbourne for a global AIDS conference along with dozens of others on the flight that ended in tragedy on Thursday.

Rescue workers at the crash site of Malaysian airliner MH17 in eastern Ukraine told an Agence France Presse reporter Friday that they had found one of the black boxes from the passenger liner.

Emergency crews were working through the debris of the downed jet that was spread out across an area stretching for kilometers while rebels controlling the area have pledged to allow international investigators access to the site.

The downing of a Malaysia Airlines passenger jet with 298 people aboard heaped new distress on a nation still stung by the trauma and global stigma of flight MH370's disappearance four months ago.

The United States said Thursday that Russia's support for separatists in Ukraine created the conditions in which a Malaysian airliner was apparently shot down with the loss of nearly 300 people.

Malaysian maritime authorities found two more bodies floating in the sea Wednesday after a boat carrying illegal Indonesian migrants sank, raising the confirmed death toll to four with seven still missing.

The fiberglass boat, believed to be carrying 72 people, capsized late Monday off the southern state of Johor.

Pirates have attacked a Malaysian tanker and stolen the gas oil cargo before releasing it in the latest attack in Southeast Asian waters, officials said on Wednesday.

The MT Oriental Glory was hijacked late Tuesday in the South China Sea off southeast Malaysia, the navy said in a statement.