At least "four or five" suspects and handlers involved in the suicide bombing attack in Islamabad have been detained, Pakistan's Interior Minister Rana Sanaullah has claimed.

A policeman along with two suspected militants were killed and at least six others, including four policemen, injured in the bombing on Friday in the upscale residential area, barely 15km away from the garrison city of Rawalpindi, where Pakistan's powerful military establishment is located.

"We have arrested the suspects of the Islamabad terrorist attack and have also detained their handlers," Sanaullah announced in an overnight tweet.

His tweet showed that the second person in the vehicle was not a woman, as police initially said, but was the taxi driver hired by the suicide bomber for transportation from Rawalpindi to Islamabad.

"The taxi driver was innocent and had no role in the attack. The terrorists moved from Kurram Agency (tribal district) and stayed in Rawalpindi. We have detained four or five suspects," he said.

The city has been on high-security alert since the attack and police have announced a raft of measures, including 25 new check-posts, to counter any new threat by the terrorist.

As the terror spread in the city, many foreign missions, including the United States and Saudi Arabia cautioned their nationals to restrict their movements.

The bombing was claimed by Tehreek-e-Taliban Pakistan (TTP)—a banned terrorist group that has reactivated after the capture of Kabul by the Afghan Taliban.

The TTP, believed to be close to al-Qaeda, has been blamed for several deadly attacks across Pakistan, including an attack on army headquarters in 2009, assaults on military bases, and the 2008 bombing of the Marriott Hotel in Islamabad.

In 2014, the Pakistani Taliban stormed the Army Public School (APS) in the northwestern city of Peshawar, killing at least 150 people, including 131 students.

The Friday attack was the first suicide bombing incident in Islamabad since the 2014 courthouse bombing that killed 10 people.

Pakistan authorities on Saturday set up a four-member joint investigation team (JIT) to probe a suicide bombing in the capital as the country undertook a policy review to deal with the latest threat by militants.

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