Sheikh Hasina has ordered an investigation

The blast, which took place in the Gopalganj district - 100km (62 miles) south of the capital, Dhaka - has also left at least 20 people critically injured.

Officials say about 70 people were attending Sunday prayers when the bomb went off.

It is believed to be the first such attack on a Catholic church in Bangladesh. No group has said it planted the device.

No threats

The bomb went off as people were attending Sunday prayers at the Baniarchar Christian mission, said Jawadul Karim, press secretary to Prime Minister Sheikh Hasina.

She said the prime minister had ordered an investigation into the incident and asked army explosive experts to visit the area, which is near her hometown.

The Archbishop of the Roman Catholic Church in Bangladesh, Michael Rosario, said they had not received any threats and there was no report of any communal tension in that area.

He described the attack as barbaric.

Archbishop Rosario said they were taking the attack seriously and hoped the government would take appropriate steps to find out who was responsible.

Christians account for about one percent of Bangladesh's 130 million people, most of whom are Muslim. Baniarchar has a "large" number of Christian residents, police inspector Shah Alam said.

But correspondents say religiously motivated violence against Christians is rare.

Last April, a bomb attack at a concert in Dhaka during the Bengali New Year celebrations killed nine people.

The government blamed Islamic extremists for that attack.