Two Christians accused of blasphemy in Pakistan were killed as they left a courthouse Monday afternoon, reports a Christian persecution watchdog group shortly after the incident.

Police were transporting Pastor Rashid Emmanuel and his brother, Sajid Emmanuel, from the court in Faisalabad to jail when masked gunmen opened fire, killing the two Christians and seriously wounding a policeman accompanying them before getting away, reported Washington-based International Christian Concern.

The brothers had been arrested on July 2 after being accused of writing a pamphlet with blasphemous remarks about the Muslim Prophet Muhammad – a crime punishable by death in Pakistan.

They had just made a court appearance when Monday’s attack took place.

“It’s outrageous that the Islamists managed to kill the Christians while they were under police custody,” said Jonathan Racho, ICC’s regional manager for South Asia.

“This is another indication of the value and status of Christians within Pakistan.

"We call upon the international community to hold Pakistan responsible for its mistreatment of Christian minorities.”

While the US State Department noted in its last report on religious freedom in Pakistan that the Islamic republic took some steps to improve its treatment of religious minorities during the reporting period, it said “serious problems remained”.

“Authorities routinely used blasphemy laws to harass religious minorities and vulnerable Muslims and to settle personal scores or business rivalries,” the department reported.

Furthermore, it added,“[m]obs occasionally attacked individuals accused of blasphemy and their families or their religious communities.”

“When blasphemy and other religious cases were brought to court, extremists often packed the courtroom and made public threats against an acquittal,” the department noted. “Religious extremists continued to threaten to kill those acquitted of blasphemy charges. High-profile accused persons often went into hiding or emigrated after acquittal.”

In the case of the slain Pakistani Christian brothers, the families of the men have maintained their innocence and the minister of minority affairs, Shahbaz Bhatti, said he suspected the men were falsely accused of blasphemy by people with a grudge against them.

"I personally don't think that anyone who wrote derogatory things against Muhammad would put their names on the bottom," he told The Associated Press. "This was just to settle a personal issue."

Muslims make up an estimated 97 per cent of Pakistan's 180 million people.