Three women dressed in burqas killed a man who had been accused of blasphemy in 2004 in a northeastern Pakistani town, police said on Thursday, the second brutal killing over alleged insults to Islam in a week.

Blasphemy is a highly charged topic in Pakistan where there have been at least 66 murders over unproven allegations since 1990 according to figures from a Centre for Research and Security Studies report and independent records kept by Reuters.

The country's strict blasphemy laws carry sentences ranging from small fines to the death penalty.

The women entered the home of Fazal Abbas, a faith healer and a leader of the minority Shia community in the small city of Sialkot, and asked him to perform a spiritual ritual during which one of them shot him in the chest, police told Reuters.

Abbas was accused of blasphemy in 2004 by members of a hard-line conservative group after which he fled to Denmark, his cousin Azhar Hussain and police inspector Nadeem Afzal said.

"He returned recently with the conviction that he would prove his innocence in court and had been granted bail by a local judge," Hussain said.

Police say that one of the women acted as an instigator, persuading the other two to carry out the act and identifying Abbas as a blasphemer.

"It is their personal act, and I could not find their link to any religious group," inspector Afzal said.

However, Abbas' family believe that a hard-line religious group incited the women to track down their victim and pull the trigger.

On April 13 a mob beat student Mashal Khan to death when blasphemy accusations spread across a university campus in the northern city of Mardan. Police are now investigating a number of university students and faculty for their involvement in a brutal attack that shocked the entire nation. 

In 2011, a bodyguard assassinated Punjab provincial governor Salman Taseer after he called for reforming blasphemy laws.

Taseer's killer, executed last year, has been hailed by religious hardliners as a martyr to Islam and a shrine has been erected at his grave.

Recently, fighting blasphemy has also become a rallying cry for the government.

Prime Minister Nawaz Sharif issued an order last month for the removal of blasphemous content online and "strict punishment" for those found guilty of posting such content.