A British oil executive has been shot dead in front of his wife in what appears to have been an assassination-style killing in Belgium.

Nicholas Mockford, 60, an executive for ExxonMobil, was gunned down as he left an Italian restaurant in a suburb of the capital Brussels.

He was shot three times, once as he lay on he floor, and his wife Mary was left beaten and covered in blood, cradling her husband and shouting for help. He died on the way to hospital.

Witnesses say they saw the couple walk across the street to their Lexus car before shots were fired. Reports suggest two men were spotted running away from the scene, one holding a motorcycle helmet.

The shooting is understood to have happened on October 14, but news about the attack has only emerged now after Belgian police imposed a news blackout, reports said.

The Daily Telegraph said police in Belgium were considering all possible motives for the shooting, including a carjacking, although Mr Mockford's car was not stolen.

The Belgian prosecutor's office said on Thursday night that there was a "judicial instruction" from Martine Quintin, the investigating judge, that meant they could give no "explanation" and no detail about the killing, which a spokesman said was "usual in such a serious murder investigation", the Telegraph reported.

However, Chief Inspector Wim Van Leifferenge said the killing had been reported by media in the country since it happened.

Mr Van Leifferenge said no-one had been arrested and those responsible were still on the run.

A Foreign Office spokesman said: "We can confirm the death of a British national in Brussels on October 14 and we are providing consular assistance."