Up to 25,000 supporters caused chaos in Pakistan when they protested in support of a man who was executed after he murdered an opponent in the long-running dispute over the country's blasphemy laws.

Mumtaz Qadri was hanged last month for the murder of Salman Taseer, governor of Punjab, who had opposed the blasphemy laws. The protestors at the rally called repeatedly for Qadri to be declared a martyr.

The protests came hours after extremists murdered 72 people and injured scores more in a suicide bombing in a park in Lahore on Easter Sunday.

The Qadri protest began in Rawalpindi. The marchers then broke through barriers to access Islamabad's "red zone", The Times of India reported. Most went home but several thousand stayed a second day for a sit-in outside parliament. More than 40 security officials were injured as well as 16 civilians. There were some arrests for vandalism. 

Besides wanting Qadri recognised as a martyr, with a public holiday in his name, the protestors also want the blasphemy laws to be toughened up, with executions for all those convicted.

Among those on their hit list is the Christian woman Asia Bibi, who is currently on death row on charges of blasphemy. She was among those who Taseer tried to save. Her sentence was suspended awaiting appeal last year and since the execution of Qadri, security in her prison has been tightened. She is said to be cooking all her own food in an attempt to avoid being poisoned.