Four killed as police fire on Bangladesh protesters

20,000 Muslims protested against a Facebook post said to have defamed the Prophet Mohammed

Some of the at least 50 wounded being treated in hospital after police said they opened fire in self-defence when some of the crowd threw rocks at officers. AFP

Bangladeshi Prime Minister Sheikh Hasina on Sunday called for calm after at least four people were killed when police fired on thousands of Muslims protesting against Facebook messages said to have defamed the Prophet Mohammed.

Twenty-thousand Muslims demonstrated at a prayer ground in Borhanuddin town, 195 kilometres from the capital Dhaka, after a young Hindu man was charged with inciting religious tension through online messages.

Police said they opened fire in self-defence after some of the crowd threw rocks at them. Up to 50 people were injured.

The death toll is expected to rise, with local doctor Tayebur Rahman telling AFP at least seven of the 43 people taken to hospital were fighting for their lives.

Ms Hasina said the Facebook account of the man charged with inciting religious tension was hacked by a Muslim person and used to "spread lies".

"We saw rumours are being spread in Facebook to create an environment of anarchy. Who are they? What is their intention?," she told her political party's members.

"I asked our countrymen to have patience. And those who want to fish in troubled waters, we will find them and take action against them."

Bhola's deputy police chief Sheikh Sabbir said the man went to the police station on Saturday claiming his Facebook account was hacked.

"We also suspect that his account was hacked and these contents were spread through Facebook messenger," Mr Sabbir said.

But the charges have not been dropped.

Extra police and border guards were rushed to the island on helicopters.