PESHAWAR, Pakistan - The leader of the Pakistani Taliban, the militant movement that poses the gravest security threat to the country, is believed to have been killed by a US drone strike, four Pakistan intelligence officials said on Sunday.

Taliban leader Hakimullah Mehsud (L) sits beside a man who is believed to be Humam Khalil Abu-Mulal Al-Balawi, the suicide bomber who killed CIA agents in Afghanistan, in this file still image taken from video released January 9, 2010. [Photo/Agencies]

The officials said they intercepted wireless radio chatter between Taliban fighters detailing how Hakimullah Mehsud was killed while travelling in a convoy to a meeting in the North Waziristan tribal region near the Afghan border.

A senior military official told Reuters there was no official confirmation that the Pakistani state's deadliest enemy had been killed. The Pakistani Taliban issued a denial. US officials, speaking to Reuters on condition of anonymity, could not confirm his death.

If Hakimullah did die, it could ease pressure on security forces, who have struggled to weaken the group, which is close to al Qaeda and has been blamed for many of the suicide bombings across one of the world's most unstable countries.

"Six to seven TTP members were talking to each other through wireless radio in the conversations we heard, talking about Hakimullah Mehsud being hit by a drone when he was heading to a meeting at a spot near Miranshah," said one of the intelligence officials.

"They referred to him by his codename."

Officials refused to disclose Mehsud's codename.

"Based on our intercepts, Mehsud was heading to a meeting in Nawa Adda," said another intelligence official. Nawa Adda is a village in the Dattakhel area of North Waziristan.