Station Chief Inspector Ajmeer Shah, who had arrested and killed several militants, and driver Taqrimul Haq were pronounced dead at the scene where their car had slowed down to negotiate a speed bump.
Six passers-by were also injured -- two critically -- in the blast around noon near a central market in the city of Risalpur in Khyber Pakhtunkhwa province, around 30 miles east of Peshawar and 60 miles from the Khyber Pass.
In a telephone call to reporters in Peshawar, a man claiming to be a spokesman for the rebel group Tehrik-e-Taliban Pakistan said the TTP was responsibility for the attack and will carry out more suicide attacks, a report in The Nation newspaper said.
"Our target was Ajmeer Shah who had killed our commander Jannat Gul in a raid in Akora Khattak last month," the TTP spokesman said.
Shah, 36, was born in the district. He received the Presidential Pride of Performance Award for his part in tracking down Gul and for foiling many attempted terrorist attacks. For his efforts Shah had been receiving regular death threats from suspected terrorists.
Gul, who also went by the names Jamaluddin and Qari Basit, was killed in a shootout with police in late September.
Gul was wanted by police for his involvement in a bomb attack in the northwestern garrison city of Kohat. He was also blamed for a militant attack on police in Peshawar in August to free convicted Taliban commanders Zaqeem Shah and Nadeem Abbas.
Three policemen were killed in the August attack carried out when a police team was taking the Taliban commanders from their prison to a dentist.
Also in August, a bomb blast in Nowshera district targeted Pakistani military personnel at a restaurant, killing 10 people, including several air force personnel.
Shah entered the police force as a constable in 1995 and was later appointed an instructor at the Police Academy in the city of Hangu, northwest Pakistan. He later served in Peshawar before transferring to Risalpur and marrying last year.
TTP leaders hope to impose a strict interpretation of Koranic instruction throughout Pakistan and to expel Coalition troops from Afghanistan.
Islamabad has blamed TTP for most attacks within Pakistan, including the assassination of former Prime Minister Benazir Bhutto in December 2007, according to data from the U.S. government's National Counterterrorism Center.
"TTP also targets U.S. interests within Pakistan, claiming responsibility for arson attacks against NATO supply convoys in December 2008, a bomb blast in the northwest that killed U.S. soldiers in February 2010 and an assault against the U.S. Consulate in Peshawar in April 2010."
Baitullah Mahsud, the first TTP leader, was killed in an explosion in August 2009 and was succeeded by Hakimullah Mahsud.