Islamabad - At least seven people, including five policemen, were killed and around two dozen injured Sunday when a suicide attacker targeted a police vehicle in north-west Pakistan, a security official said.

The explosion in Dera Ismail Khan district of Pakistan's North- Western Frontier Province destroyed the vehicle.

"A suicide bomber blew himself up as a police van carrying several law enforcers reached the site of a low-intensity roadside blast near a restaurant," said a police official Sanaullah Khan.

He said the five policemen inside the van were killed and three more injured, while two civilians, including a journalist who was covering the first blast, were killed and more than 20 were injured.

It was not immediately clear whether the second blast was a suicide attack or a roadside bombing.

No one claimed responsibility for the attack, but Khan said he suspected Taliban militants based in Pakistan's tribal region for the carnage.

Dera Ismail Khan is located close to the restive tribal district of South Waziristan, a known sanctuary of Taliban and al-Qaeda fighters, launching cross-border raids on international forces in Afghanistan as well as targeting Pakistani security forces on regular basis.