Dhaka: At least four people were killed and 50 others injured as Bangladesh police on Sunday opened fire on hundreds of Muslims protesting against an alleged blasphemous Facebook post by a Hindu man.

The violence erupted in the morning after hundreds of Muslims gathered in southwestern Bhola district, 116 kilometers from Dhaka, for a protest rally under the banner of Muslim Tawhidi Janata', demanding action against the Hindu man for his social media comments against Prophet Mohammed.

The Hindu man, who is in police's protective custody, has denied making the comment, saying his Facebook account had been hacked. Following a complaint by him, police detained three people for allegedly hacking his Facebook account.

According to reports, village elders were holding a meeting with local authorities on Sunday to try to defuse the tensions that began on Friday after the Facebook post went viral. But the protesters started attacking security officials, prompting them to retaliate.

The protestors were trying to vandalise the town and attacked police, forcing us to retaliate with our guns in self defence. Four people were killed during the incident, Bhola's district police chief Sarkar Mohammad Kaisar said.

The death toll is expected to rise as some of the injured are stated to be in critical condition.

Kaisar said several policemen were also injured in the clash at Char Boharuddin area of Bhola, the biggest riverine island of the country.

Paramilitary Border Guard Bangladesh (BGB) troops have also been deployed in the area.

The violence was second such incident since 2016 in the Muslim-majority country when protestors attacked Hindu temples in eastern Brahmanbaria town after a blasphemous Facebook post.

Despite demands by hard-line Islamist groups, authorities in Bangladesh have refused to introduce tougher Islamic laws.