Former Pakistani Prime Minister Benazir Bhutto has received a new death threat just four days after an assassination attempt against her killed 139 people.

Ms. Bhutto's lawyer, Farooq Naik, says a handwritten letter was sent by someone claiming to be a friend of al-Qaida, Osama bin Laden and Pakistani extremists. The authenticity of the letter has not been confirmed.

Ms. Bhutto's Pakistan People's Party says it is taking the threat seriously. The twice-serving former prime minister survived an assassination attempt last Thursday when suicide attackers struck near her convoy as it drove through the packed streets of Karachi hours after she returned to Pakistan, ending years of political exile.

Ms. Bhutto has said extremist elements in Pakistan's political establishment were behind the attack.

She also has accused the government of having something to hide after the interior minister, Aftab Sherpao, rejected her call for international experts to help with the investigation.

The government proposed Monday that mass political rallies be banned for security reasons. Opposition political parties have rejected the plan.

Investigators have said they suspect two suicide bombers were responsible for the attack.

Some information for this report was provided by AFP, AP and Reuters.