A suicide bomb attack has killed at least four people and injured a dozen more in the north-western Pakistani city of Peshawar, officials say.

巴基斯坦西北部城市白沙瓦发生一起自杀式炸弹袭击，至少4人死亡、12人受伤。

Correspondents say CCTV footage shows the bomber¹ detonating引爆，激起 his explosives as he passes through a checkpoint检查站，关卡.

Peshawar has borne the brunt of首当其冲 recent attacks, which have left hundreds dead. This was the second bomb in three days.

Pakistan has seen a surge巨涌 in violence since the army began an offensive against the Taliban in Waziristan.

The latest suicide attack struck a busy commercial road in the main Saddar area of Peshawar, near the offices of Pakistan's national airline and an area where the military live.

"I can see smoke and injured people lying on the ground," one witness, Shahid Khan, told the AFP news agency from near the scene.

TV footage from the scene showed shattered glass and debris碎片，残骸 covering a wide area.

A senior minister for the North West Frontier Province, Bashir Ahmad Bilour, told the media that four people had been killed, including two policemen, in what he said was a suicide attack.

The BBC's Abdul Hai Kakar in Peshawar says the bomber was on foot and heading towards the busiest market in the heart of the city when he was stopped by police and blew himself up.

Residents are living in fear of more bomb blasts, our correspondent says, and are trying to limit their movements around the city wherever possible.

The latest blast comes only two days after a suicide bomber killed three in an attack on a journalists' club in Peshawar.

Holy month

The BBC's Aleem Maqbool in Islamabad says that officials plan to effectively seal off Peshawar from Thursday evening through to直到 the middle of next week.

There are fears the climax³高潮，顶点 of the Muslim holy month of Muharram in the coming week will bring more bloodshed流血，杀戮, our correspondent says.

Peshawar, near the Afghan border, has been targeted repeatedly since the Pakistani army operation in South Waziristan began in mid-October.

In late October, at least 100 people died when a huge car bomb ripped through the city's busy Peepal Mandi market.

More than 500 people have been killed in attacks across the country since the army operation began in the autumn.