Pakistan police say violence erupted at a rally convened by Islamists in favor of the country's harsh blasphemy laws in the city of Lahore.

Wednesday's rally coincided with the commemoration for a former governor killed for supporting a Christian woman accused of blasphemy.

Senior police officer Haider Ashraf says 76 demonstrators were detained as they tried to reach the family residence of Salman Taseer, the ex-governor killed in 2011 by his bodyguard for backing Asia Bibi. She had been on death row for years.

Ashraf said officers used tear-gas to disperse the rally.

On Tuesday, one of Taseer's sons, Shan Taseer, angered Islamists by urging people on Twitter to pray for Bibi. Under Pakistan's blasphemy laws, anyone found guilty of Insulting Islam can be sentenced to death.