An Al Qaeda leader with a bounty of a million dollars on his head was killed in a US drone strike in Pakistan's lawless tribal belt earlier this week, security officials said on Saturday.

Atiyah Abd al-Rahman, an Al Qaeda operative of Libyan origin, died in a missile strike on Thursday, said the officials who spoke on condition of anonymity.

Rahman was killed with three other militants when the unmanned spy plane fired two missiles at a vehicle in North Waziristan Agency, which borders Afghanistan.

The US had earlier offered a bounty of one million dollars for Rahman.

The officials said another lower ranking Al Qaeda operative, Khalid Mohammad Abbas al-Harabi, too was killed in the same missile strike.

The US has significantly stepped up drone attacks in the Waziristan region since early September.

The increase in strikes coincided with reports that Western intelligence agencies had uncovered a plot by militants based in the region to attack major European cities.