LAHORE, Pakistan (Reuters) - Six people were killed and at least 20 were buried under rubble when a large blast destroyed the home of one of Pakistan's provincial ministers on Sunday, rescue officials said.

Police said the blast appeared to be a large bomb, and it had caused the roof to cave in as the home minister of Punjab province, Shuja Khanzada, held meetings with supporters in his hometown of Attock in northern Pakistan.

Punjab, Pakistan's biggest and wealthiest province, is the political heartland of Prime Minister Nawaz Sharif.

"There were between 20 and 30 people present when the blast took place," district information officer Shahzad Niaz told Reuters. "The roof collapsed."

Rescue workers at the scene said six bodies had been recovered so far.

There was no immediate claim of responsibility. Pakistan, a nuclear-armed nation of 190 million people, is plagued by a Taliban insurgency, criminal gangs and sectarian violence.

Punjab has traditionally been more peaceful than other parts of Pakistan. Sharif's opponents have accused him of tolerating militancy in return for peace in his province, a charge he hotly denies.

Two weeks ago, Punjab police killed the leader of one of Pakistan's most feared militant groups, Lashkar-e-Jhangvi, along with his two sons, deputy, and 10 other supporters.

Police described the incident as a shootout as he sought to escape from custody, but many insiders say the shooting had the hallmarks of an extrajudicial killing.

(Writing by Katharine Houreld; Editing by Nick Macfie)