Islamabad, Sep 23 (IANS): A policeman was killed and three others were injured while escorting a group of diplomats travelling from Pakistan's northwest Khyber Pakhtunkhwa (KP) province to the capital Islamabad on Sunday, Pakistan's Ministry of Foreign Affairs said.

An advance scout police vehicle was hit by an improvised explosive device in Swat district of KP, which resulted in the casualty of the police, the ministry said in a statement.

The group of diplomats has returned safely to Islamabad, Xinhua news agency reported, citing the statement.

"Our sympathies are with the families of the demised policeman and three injured in the incident," the foreign office said, adding that such terrorist acts will not deter Pakistan from its commitment to the fight against terrorism.

Police sources told Xinhua that the diplomats' delegation included ambassadors, attaches, and their families, accompanied by representatives of a local commerce chamber.

No group has claimed responsibility for the attack yet.

The area had been cordoned off for further investigations.