Hundreds of thousands of Islamist devotees Friday converged on Bangladesh's biggest mosque Baitul Mukarrum to join in Ramadan-end mass prayers in the capital Dhaka amid a high security alert, officials and witnesses said.

The state-run Islamic Foundation which organized the prayers marking the last Friday of the Muslim month of fasting said over a quarter of a million people attended the Jumatul Wida congregation addressed by Muslim clerics.

Witnesses said Muslim worshippers blocked streets to the crowded national mosque located in central Dhaka to make additional space for people who did not find room inside the mosque.

However a high alert was sounded by the authorities as intelligence reports indicated a violent attack on a high profile target in the capital city during next week's Eid al-Fitr celebrations.

Dhaka's Police Commissioner Naim Ahmed told reporters that a special force of 5,000 paramilitary border guards, rapid action commandos and auxiliary police will be deployed ahead of the Muslim festival of charity.

Ahmed also enhanced security of rail and ferry stations where thousands of families are waiting to go to their hometowns for the Muslim festival followed closely by the Hindu Durga Puja celebrations.

The interim government has tightened security in the capital as the media reported a rise in crime recently.

"We will call police reserves if there is any necessity for help in maintaining law and order," Ahmed said.

Bangladesh is a Muslim majority country but has a sizeable population of Hindus and other minority groups.