Four security personnel injured in suicide attack in Pakistan's Khyber Pakhtunkhwa

One of the militants had been arrested and was being interrogated at Counter-Terrorism Department (CTD)

At least four security forces personnel were injured in a suicide attack on a military vehicle in restive northwest Pakistan on Monday, security forces said, a day after militants attacked and killed four policemen at a newly-constructed police station in the province.

A suicide bomber hit the vehicle of the security forces on the Thall bridge in the North Waziristan tribal district of Pakistan, a source said.

The forces have cordoned off the area and started a search operation to nab the culprits.

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No group has yet claimed responsibility for the attack.

The Tehreek-e-Taliban Pakistan (TTP) militant group, which has been fighting to bring the law of Sharia across the Muslim-dominated country, mostly carries out attacks on security forces.

On Sunday, heavily-armed militants attacked the newly-constructed Burgai police station in Lakki Marwat bordering the South Waziristan tribal district of Khyber Pakhtunkhwa province, leaving four policemen dead and as many injured, officials said.

Last month, militants attacked a police patrol vehicle, killing all six policemen in the same area. The Pakistani Taliban claimed responsibility for the ambush.

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The TTP, set up as an umbrella group of several militant outfits in 2007, last month called off a ceasefire agreed upon with the federal government in June and ordered its militants to stage terrorist attacks across the country.

The group, which is 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 2012, Nobel laureate Malala Yousafzai was attacked by TTP. She suffered bullet injuries and was admitted to the Military Hospital (CMH) Peshawar and then taken to London for further treatment. The TTP claimed responsibility for the attack, saying that Yousafzai was a "Western-minded girl".

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 attack sent shockwaves across the world and was widely condemned.