Islamabad - Four Pakistani soldiers were killed in a Taliban rocket attack on their camp in troubled north-western borderlands, while forces killed six militants in the retaliatory fire, officials said on Saturday.

The militants targeted army with artillery fire in Mir Ali town of the volatile North Waziristan tribal district, which borders Afghanistan and is a known hotbed of Taliban and al-Qaeda militants.

"Four soldiers perished in the artillery attack, which our forces repelled and killed six militants," an intelligence official said on condition of not being named as he was not authorized to talk to media.

Mir Ali lies on borer of the neighbouring South Waziristan, a mountainous region, where the army launched an operation last month against the militants. It was suspected that most of them had fled to North Waziristan to re-group and start guerrilla warfare.

Islamic militants have stepped up attacks on town and cities to avenge their losses in South Waziristan.

The capital of North West Frontier Province, Peshawar, has borne the brunt of many attacks.

On early Saturday, a bomb struck at the office of a Germany based humanitarian organization, Comprehensive Health and Education Foundation, on the outskirts of the city, wounding a security guard.

It was time bomb and exploded at 7.00 am near the perimeter wall of the main building, said Liaquat Ali Khan, a senior city police officer.

The bombing came a day after a roadside bomb ripped through a police patrol vehicle that killed three officers and injured another six. (dpa)