A suicide bomber aimed at employees lining up for their wages outside a Pakistan bank building and hotel on Monday, killing 24 people as the UN withdrew expatriate staff from the northwest.

A upsurge in bloodshed left over 300 people dead in September as Pakistan launches a major offensive against the Tehreek-e-Taliban Pakistan (TTP) in the tribal belt, where US authorities say Al-Qaeda are planning further attacks on the West.

A senior police figure said the attack was the actions of a suicide bomber. We found pieces of a suicide vest and some body parts of the suicide attacker, a senior police official Aslam Tarin told reporters.

Deeba Shehnaz, a rescue workers spokeswoman, also told reporters from the site that the death toll has risen to 24 with another 24 people wounded.

The blast off Mall Road was near the upmarket Pearl Continental Hotel and close to Pakistan s army headquarters, where 10 gunmen maintained a nearly 24-hour siege last month that left 23 people dead and deeply embarrassed the military. Immediately, Ishrat Rizvi, a UN spokeswoman, told AFP, unable to say immediately how many staff the decision affected. UN Secretary General Ban Ki-moon declared the world body had raised the security level to “phase four” in the North West Frontier Province and the Federally Administered Tribal Areas, a UN statement said.