A doctor, who performed the postmortem on Sudipta, said he received a fatal head injury after being hit by a blunt object but did not elaborate. The doctor said that the details will be mentioned in post mortem report to be submitted within the next 48 hours.

Thousands of Leftists joined Sudipta’s funeral procession, whose alleged death in police custody here triggered outrage cutting across the political divide. The row was triggered with the police claiming that the death of Sudipta Gupta was an accident, while the Opposition Left Front alleged he succumbed to injuries sustained during a heavy lathi-charge by police.

West Bengal Chief Minister and Trinamool Congress supremo Mamata Banerjee was on the defensive as she called the Tuesday death of Sudipta "unfortunate" and pledged to help his distraught family.

The Left Front, however, lambasted Banerjee for commenting on the death of the activist in police custody before a probe had been conducted. It also alleged that she was trying to establish the death as an "accident".

The Chief Minister visited the state-run hospital where Gupta succumbed to his injuries on Wednesday afternoon. She said many activists of her party had been killed when they crashed into lamp posts while travelling by trains.

State Left Front chairman and CPM state secretary Biman Bose said Banerjee's comment on the SFI leader's death before any inquiry was "wrong". "The Chief Minister has made some comments. She is not only a Chief Minister but also holds the Home portfolio. If she comments on the death, then is there any scope of an inquiry?" Bose told a media conference here. The SFI is the student wing of the CPI.

"Sudipta was hit on his head so hard that one of his eyes popped out," added West Bengal SFI joint secretary Shatarup Ghosh. The police, however, said that the activist died after he crashed into a lamp post while being taken to jail. Sudipta's body, wrapped in the CPI-M's red flag, was taken in a flower-bedecked hearse from the hospital to the Netaji Nagar College where he was general secretary of the students' council. Grieving students and teachers offered floral tributes amid cries of "Lal Salam!"

The body was then taken to Sudipta's residence where his father broke down. The inconsolable 63-year-old Pranab Gupta, a widower, said his son "used to dream of a new social order, a new dawn". He said he would not let the death go in vain and fight for justice.

The body of the deceased activist was then taken to the SFI state committee office, where senior Left Front leaders, including Biman Bose, former chief minister Buddhadeb Bhattacharya and leader of opposition in the state Assembly Suryakanta Mishra, garlanded the body.

The funeral procession, in which thousands of people from different walks of life participated, traversed various arterial roads and finally reached at Keoratala crematorium at south Kolkata, where the body of the SFI activist was consigned to flames.

Gupta's elder sister Sumita Sengupta, however, took a dig at the CPM, alleging that the deceased activist had been brainwashed by the party. "CPM brainwashed my brother. The leaders used him for the party's interest," Sengupta said.

Even the Congress voiced dismay. "With (Trinamool) taking over, we had thought the state will witness change. What I see is the politics of police killing students ... has come back," state Congress president Pradip Bhattacharya said.

The death in Kolkata triggered protest demonstrations in Chennai, Kerala and New Delhi. In the national capital, over 100 JNU students staged a noisy protest outside Banga Bhawan, which belongs to the West Bengal government. Some students tried to scale the boundary wall but were stopped by police.