Militant leader Saif Ullah, a key supporter of Osama bin Laden, was killed in a U.S. drone strike launched late Tuesday night in Pakistan's northwest tribal area of North Waziristan, local Urdu TV channel Dunya reported on Wednesday.

The report quoted unidentified official sources as saying that Ullah was killed together with three other suspected militants in the strike which was launched at about 11:00 p.m. Tuesday night by U.S. drones in the Mirali area of North Waziristan, a place which is believed to be a main stronghold of militants along the Pakistan-Afghanistan border area.

Late Tuesday night, U.S. drones fired four missiles at a house suspected of being a hideout of militants in the afore-said area, reportedly killing six people and injuring five others.

Saif Ullah, a 50-year-old Australian national, is believed to be a key leader of militants supporting al-Qaida. He is the second most important militant leader killed in U.S. drone strike in Pakistan since this year.

Earlier on June 3, another important militant leader Ilyas Kashmiri who was one of the top five terrorist leaders most wanted by the U.S. got killed in a late Friday night strike launched by U. S. drones in South Waziristan, another militant stronghold neighboring North Waziristan.

Ilyas Kashmiri, a native of Pakistan, is the founder and chief of Harkat-ul-Jihad al-Islam, a terrorist group affiliated to al- Qaida. The 47-year-old terrorist leader is believed to have masterminded a number of terrorist attacks in the country including the May 22 attack on a naval air base in Karachi, in which two U.S.-made P3C Orion surveillance planes and one helicopter were destroyed and a dozen security people were killed.