Islamabad - An explosion in eastern Pakistan's Lahore city has killed at least 23 people and injured over 200 others.
The explosion occurred near Civil Lines Office on Mall Road in Lahore, capital city of Punjab province.
According to District Coordination Officer in Lahore Sajjad Bhutta, the attack was a suicide car bombing.
Local press reports quoted witnesses as saying three unidentified people in a vehicle reached the police office building Wednesday morning.
Gunmen around the building then started firing and people inside the vehicle hurled a hand grenade at the building before ramming the explosive-laden vehicle into it.
The bomb disposal squad said around 100kg of explosives were used in the attack.
Rescue teams are engaged in relief operations while rescuers are trying to find people from the rubble. A state of emergency has also been declared in all the hospitals in Lahore, with the casualty figure expected to rise.
Although, no group claimed responsibility for the blast, police have arrested two suspects at the site of the blast.
Security in the capital Islamabad and the adjoining 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.