Washington, Aug 7 - The US government has begun an investigation into whether Pakistan Taliban chief Baitullah Mehsud, who is said to be responsible for the assassination of former prime minister Benazir Bhutto, was killed in a drone attack Wednesday, senior officials have said here. DNA tests will be carried out to determine if indeed Mehsud has been killed.

Earlier reports had indicated that one of the wives of Mehsud had been killed in the drone strike in northwestern Pakistan's South Waziristan tribal agency.

US officials Thursday said they believe 'Mehsud himself may have been killed' and that both US and Pakistani teams were investigating the possibility, Wall Street Journal reported Friday.

'There is reason to believe that reports of his death may be true, but they can't be confirmed,' a US official was quoted as saying.

Mehsud was considered one of the most wanted Islamist extremists in Pakistan's western tribal regions, leading a large army of militants that have fought US and Pakistani forces on both sides of the Afghanistan-Pakistan border.

Pakistani officials have accused Mehsud of being behind a number of high-profile terrorist attacks, including the assassination of former prime minister Benazir Bhutto in 2007.