Islamabad  - At least 15 people, including a school girl and three soldiers, were killed Wednesday in a suicide bombing and clashes between Taliban militants and security forces in various parts of Pakistan, officials said.

A pedestrian suicide bomber blew up near a convoy of six to seven vehicles carrying paramilitary Frontier Corpse (FC) personnel in Quetta, the capital of the north-western province of Balochistan.

"Thirteen FC personnel and one passerby were injured while four schoolgirls were also wounded. One of the girls later on expired at the hospital," Asif Nawaz, Quetta police chief, told Geo news channel.

The attack came as authorities have put security at high alert following Saturday's truck suicide bombing at Islamabad's Marriott Hotel, where 53 people including two US Marines and the Czech ambassador died and more than 250 were injured.

Nawaz said police had taken measures to ensure security but "it is not easy to stop a person who has already put his life at stake."

The western parts of Balochistan which border Afghanistan are centres of Taliban militant activities and some media reports have suggested that some senior leaders of the Afghan Taliban are hiding in Quetta.

Meanwhile, a roadside bomb hit a security vehicle in Charbagh area of restive Swat valley in North Western Frontier Province (NWFP), killing two soldiers and injuring one more.

Previously a popular tourist destination, Swat district, is experiencing intensive fighting since last October when Islamabad dispatched thousands of soldiers to quell the rebellion of radical cleric Maulana Fazlullah and his thousands of followers, who had launched a campaign to enforce Taliban rule in the region.

Six more people died in the tribal district of Mohmand Agency, which borders NWFP capital Peshawar. Two militants and a soldier were killed in ground clashes between the sides in Bakakhund area, while three drivers died when gunship helicopters shelled a truck convoy by mistake.

Separately, the government forces successfully cleared Darra bazaar and adjacent areas of militants in semi-tribal Darra Adamkhel district, located some 15 kilometres south of Peshawar, and killed six insurgents, a military spokesman Major Murad Khan said.

"Large cache of arms and ammunition, fake currency, passports and identity cards were recovered from the house of Matten, a known local miscreant leader during operation," he added.

The military offensive in the district was launched on Monday to re-take control over a strategic road tunnel linking Peshawar to the central and southern parts of the country.

Fifty militants and one soldier were killed in the first two days of the operation, the army claimed on Tuesday. (dpa)