Pakistani activists of Sunni Tehreek shout anti-Taliban slogans during a protest rally in Lahore on Feb. 28, 2014. The Pakistani Taliban announced a truce Saturday. Arif Ali/AFP/Getty

A spokesman for the Pakistani Taliban said Saturday that the group will observe a one-month cease-fire as part of efforts to negotiate a peace deal with the government.

Spokesman Shahidullah Shahid emailed reporters a notice saying the top leadership of the group has instructed all of its units to comply with the cease-fire.

The announcement follows Pakistan’s airstrikes in recent days against fighters' hideouts in the northwest, after previous efforts at negotiations broke down when a faction announced it had killed 23 Pakistani troops.

The Pakistani Taliban has been trying for years to overthrow the government and establish its own hard-line form of Islam across Pakistan. Tens of thousands of people have died in militant attacks.

Meanwhile on Saturday, armed fighters killed 12 members of the security escort for a polio vaccination team in northwestern Pakistan, detonating a roadside bomb before opening fire on the convoy, officials said.

The attack lasted an hour and when rescuers approached the scene the gunmen also attacked them, said Khan Faraz, an official in the Jamrud area of Khyber, a rugged tribal region bordering Afghanistan.

About a dozen wounded were taken to a hospital, but others died on the road waiting for help to arrive, he said.

Another official, Assistant Political Agent Jehangir Azam, said all the casualties were members of the levies or Khasadar, both locally recruited government-backed militias. They were providing security for the health workers.

Polio vaccination teams are frequently attacked in Pakistan, as are government security forces. A spokeswoman for UNICEF said it was unclear who was the target on this occasion.

Some religious leaders have denounced the multibillion-dollar vaccination campaign as a cover for spying or a plot to secretly sterilize Muslim children.

Al Jazeera and wire services