Masked gunmen shot dead up to 18 Christians and a policeman at Sunday prayers in an unprecedented attack in the central Pakistani town of Bahawalpur, witnesses said.
Six men on three motorcycles rode up to Saint Dominic's Church and pulled out AK47 assault rifles from bags, one witness said.
They were carrying the bags and when they came they took out guns, the witness said.
They shot two police guards before entering the packed church firing indiscriminately, killing one.
Police have been posted at Christian churches since the deadly September 11th attacks on the United States that have blamed on Saudi-born Osama bin Laden, sheltering in Afghanistan under the protection of the ruling hardline Taliban.
Christians account for about one per cent of Pakistan's 120 million population.
"Women were among the dead, said a police deputy superintendent. Dozens of worshippers were wounded, some seriously," he added.
"It is a security failure," Pakistan's minister for minorities affairs Mr S.K. Tressler told reporters.
He said the Christians of the area had been receiving threats for the past few days.
"They (administration) should have properly reacted to these threats, Tressler said before heading for Bahawalpur, along with minister for religious affairs Mehmood Ghazi, to comfort the bereaved families. It is the work of anti-state elements and fanatics," he said without elaborating.
It was the first such attack on Christians in the region, he said. The area, south of Multan near the Indian border has a history of strife between Sunni and Shi'ite Muslim extremists. Up to 1,200 Muslims have died in sectarian strife in the last nine years.
A witness said the police guards were asleep when the unidentified attackers rode up.
After shooting the policemen, four gunmen entered the church while two waited outside to shoot those who mananaged to flee, he said.
Saint Dominic's is a Catholic church but a Protestant service was being held at the time of the attack.
In 1997, Muslim rioters in southern Punjab sacked 13 churches and a school and burned and looted hundreds of houses, saying some Christians had committed blasphemy by throwing torn pages of the Koran into a mosque.
A 1986 law that makes blasphemy against the Prophet Mohammad punishable by death has been used to intimidate religious minorities, including Christians, rights groups say.
Around 2,500 people are said to be in jail or to face charges for blasphemy.
Meanwhile, three people were killed and 18 wounded when a bomb exploded on a bus in Pakistan's southwestern city of Quetta.
The explosives fitted in a transistor radio went off as the bus was passing through an area of the city that has been subject to a tribal dispute. The bus was on its way to Hanna Hurak lake, some 10 km from Quetta.
Two people were killed on the spot while the third victim died in hospital. No one claimed responsibility for the attack in the capital of Baluchistan province bordering Afghanistan.
Quetta has seen sporadic rocket attacks because of territorial disputes between local tribes.
It is premature to say who is responsible but we are looking into all aspects, including Taliban, refugees and Northern Alliance, provincial police chief Shoaib Suddle said.