A car bomb near the home of a Pakistani provincial government minister killed 20 people yesterday, a police official said, in another sign authorities are struggling against Taliban militants bent on grabbing power.

Militants who want no Western influence in nuclear-armed Pakistan, which Washington sees as critical in the battle against Islamist hardliners in Afghanistan, have not let up attacks, despite security crackdowns in their strongholds.

The blast took place in the town of Dera Ghazi Khan in a market, the kind of site frequently targeted by militants seeking to inflict maximum casualties.

"It was near a market and several shops have collapsed," said Tariq Gurmani, a resident of the Punjab province town, adding he had seen several wounded people.

The attack was another potent reminder President Asif Ali Zardari's weak civilian government has yet to devise a strategy to defeat militants who want to tightly control society - with public whippings and executions of those deemed immoral.

"It was a car bomb. About 20 people have been killed and 50 wounded," senior police official Mubarak Ali Athar told reporters.

Militants have killed hundreds of people in bombings since an October clampdown in South Waziristan - part of what is seen as a global hub for militants - that authorities said dealt a major blow to the Taliban.

The military has ruled for more than half of Pakistan's 62-year history and no civilian government has ever served out a full term, earning the country the reputation of an unstable state.

The all-powerful army is seen as the institution best able to unite politically turbulent Pakistan during crises, even though military coups have hurt the country's democratic credentials.

But its vulnerability to increasingly daring militants became clear this month when suicide bombers and gunmen killed at least 40 people in an attack on a mosque near army headquarters, 30 minutes from the capital Islamabad.