A suicide bomber rammed an explosives-laden pickup truck into a government paramilitary base in Pakistan's largest city on Thursday, causing a huge blast that killed two and wounded at least 24.

The attack on the Rangers complex in a northern suburb of Karachi came early in the morning when many residents were asleep and offices were yet to open.

Karachi is in the grip of a long-running wave of sectarian, ethnic and political violence and Thursday's attack comes as the city's main political party, the Muttahida Qaumi Movement (MQM) is urging the government to tackle Taliban elements in the city.

Rangers spokesman Major Sibtain, who uses only one name, told AFP that two of the 21 Rangers wounded when the bomber rammed the entrance to the complex had died in hospital.

"We can confirm that two of our soldiers have been killed and and 19 others wounded in the attack this morning. There is one soldier in a critical condition," he said.

Senior police official Khurram Waris told AFP that four civilians and a police officer were among the wounded.Blast amid tight security

The provincial police chief said that it was a suicide attack and only the tight security measures in force at the base had prevented major loss of life.

"It seems it was a suicide attack. The vehicle exploded before the gate of Rangers' complex because it could not enter inside due to high security," Fayyaz Lagahari told AFP.

The flatbed pickup truck was loaded with up to 150 kilograms of explosives, senior investigating officer Javed Odho told the Geo television station.

Odho said that buildings inside the complex and around it had been damaged by the blast.

MQM has called an unofficial national "referendum" next week to ask voters whether they want Pakistan to follow the ideology of the Taliban or the vision for the country imagined by its founder Mohammed Ali Jinnah.AFP