At least six people died and dozens fell unconscious due to suffocation during a Muharram procession in Pakistan's Sindh province on Monday.

An Edhi Trust official said the incident occurred in Rohri town because of the stifling heat, humidity and the size of the procession that grew and it moved closer to the main Imambargah.

Six of the mourners in the procession passed away due to suffocation while dozens also fell unconscious or ill and were taken to hospital, the official said.

Muharram is the first month of the Islamic calendar. The 10th day of Muharram is known as Ashura. It is a day of bereavement, when Shia Muslims observe fasts, take out rallies and pray in remembrance of Prophet Mohammed's grandson Imam Hussain, who was martyred centuries ago at Karbala in Iraq.

Processions are taken out in all small and large cities of Pakistan on the 9th and 10th day of Muharram which are public holidays.

Thousands attend the main processions on the 9th of Muharram and Ashura across the country with thousands of policemen and paramilitary rangers deployed to provide security.