AT LEAST nine Britons were on board Malaysia Airlines flight MH17, according to the airline.
Some 298 people were on board the Boeing 777, which crashed in eastern Ukraine on Thursday afternoon after taking off from Amsterdam for Kuala Lumpur.
PM David Cameron is to chair a meeting of the government's Cobra emergency committee to discuss the situation.
The UK Foreign Office has also set up a helpline on 020 7008 1500.
It said anyone concerned could also text MH17 to +44 7860010026, or fill in an online form at https://overseas-crisis.service.gov.uk.
The Boeing 777 came down between Krasni Luch, in Luhansk region, and Shakhtarsk in the neighbouring region of Donetsk - 50km from the Russia-Ukraine border.
Both sides in Ukraine's conflict have accused each other of shooting down the plane with a missile.
A statement on the Malaysia Airlines website said nine of the passengers were from the UK, with 41 nationalities listed as "unverified".
Foreign Secretary Philip Hammond said he was "deeply shocked" by the "appalling incident" and did not want to speculate on the causes.
The UN Security Council will also meet to discuss the incident at 15:00 BST.