The man walked up to police outside the High Court in the city of Lahore and set off explosives.

Police initially said 22 people had been killed, but police chief Malik Mohammad Iqbal said the toll had been revised down to 19, of which 16 were policemen.

The attack was the latest in a wave of violence that has killed hundreds of people in recent months, including opposition leader Benazir Bhutto, assassinated in a gun-and-bomb attack on Dec 27.

The Thursday blast has compounded fears of insecurity weeks before Feb 18 elections that could weaken President Pervez Musharraf's grip on power.

The elections are meant to complete a transition to civilian rule in the nuclear-armed US ally.

'We have found the head and legs of the bomber but they are in very bad shape because he used very high explosives,' said Lahore police chief Iqbal.

'We are trying to establish his identity. We have sent his limbs for DNA tests.'

The attack was the first suicide blast in Lahore for more than two years and has added to fears that militants are expanding their campaign out of the northwest, where they have been battling troops in areas along the Afghan border.

Lahore is Pakistan's political nerve centre and the capital of its richest and most populous province.

Stock investors cautious
A security official said the bomber was presumed to be a member of a militant group but authorities were not jumping to conclusions about which group he might have belonged to.

'The police department has asked three intelligence agencies to help them out in identifying the terrorist and his outfit,' said the security official, who declined to be identified.

The government blamed Al-Qaeda-linked militants intent on destabilising the country for the recent wave of attacks, including Ms Bhutto's assassination.

'It's too early to say who was involved but it's certainly part of the same wave of suicide bombings,' said Interior Ministry spokesman Javed Iqbal Cheema.

Pakistan's main stock index ended 1.19 per cent lower with worries about rising violence hurting trade, dealers said.

Next month's elections are for a lower house of parliament from which a new prime minister and government will be drawn and assemblies in Pakistan's four provinces.

They were meant to take place on Jan 8, but were put off after Ms Bhutto's killing.

Some analysts and politicians fear Mr Musharraf might seize the opportunity to put off the elections again, citing rising violence, with the party that backs him facing losses in the vote, especially after Ms Bhutto's murder.

Campaigning has not resumed since Ms Bhutto was assassinated and some political leaders are lying low because of security worries.

The attack came as Pakistan braced for another wave of violence as minority Shi'ite Muslims begin an annual mourning period marred by sectarian attacks in recent years. -- REUTERS