An explosion took place in eastern Pakistan's Lahore city on Wednesday, killing at least 23 people, private DAWN NEWS TV channel reported.

The explosion occurred outside the Police Emergency Services Office on Fatima Jinnah Road in Lahore, capital city of Punjab province, said the report.

At least 23 people were killed and over 200 others were injured in the blast.

Local press reports quoted witnesses as saying that three unidentified people in a vehicle reached the police office building Wednesday morning. Then gunmen around the building started firing and then the people inside the vehicle hurled a hand grenade at the building before they rammed the explosive- laden vehicle into it.

Bomb disposal squad said around 100 kg explosives were used in the attack.

The rescue team is engage in relief operation and the rescuers are trying to find people from the rubble. Emergency was declared in all the hospitals in Lahore.

The casualty figure is expected to rise.

No group claimed responsibility of the blast. The police have arrested two suspects at the site of the blast.

Security in the capital Islamabad and the adjourning garrison city of Rawalpindi has been put on high alert in the wake of the suicide blast in Lahore.

Pakistani President Asif Ali Zardari and Prime Minister Yousaf Raza Gilani have strongly condemned the blast and ordered an inquiry.

Talking to reporters in the southern port city of Karachi, Interior Minister Rehman Malik said militants carried out such attacks in desperation.

Militants earlier threatened that they would conduct attacks in various cities in the country unless the security forces ceased the ongoing military operation in the northwest against them.

The security forces launched a large-scale operation against Taliban and other militants in some parts of North West Frontier Province and over 1,000 militants have been killed in the operation so far.

(Xinhua News Agency May 27, 2009)