CPI-M MLA Gouranga Chatterjee received head injuries and was taken to hospital as also two TMC MLAs, Mahmuda Begum who was hit in the chest, and Pulak Roy who was injured in the leg.
Trouble broke out after Question Hour when an adjournment motion by Left members on mushroom growth of chit funds in the state was admitted, but a discussion disallowed.
Leader of the Opposition Surya Kanto Mishra belonging to the CPI-M rose and said that the motion had been severely edited and that the Opposition was not being allowed to speak. Left members then rushed to Speaker Biman Banerjee's podium and encircled it shouting slogans.
Assembly security staff took up positions around the Speaker and senior ministers Partha Chatterjee, Subrata Mukherjee and Firhad Hakim and Government Chief Whip Sobhandeb Chattopadhay were seen shielding the Speaker.
The Speaker went on with the business of the House including the Mention Hour amidst the din. But the situation soon degenerated into an ugly melee, with legislators from the Left and ruling party locked in scuffles and gesticulations.
Angry exchanges followed after CPI-M MLA Nazmul Haq tried to grab the Speaker's mike but a lady assembly security staff prevented him from doing so.
Chattopadhay said the mike and the light on the Speaker's table were damaged, while the mobile phone of TMC member Ashok Ghosh was stolen.
Treasury MLAs later claimed that there were attempts to attack the Speaker.
Amidst the uproar the Speaker adjourned the House till 1:30 pm and left, but the melee continued in the well for some time more.
When the House resumed at 1:30 pm, Parliamentary Affairs Minister Partha Chatterjee condemned the behaviour of the Left MLAs and demanded that the Speaker take action against them, who he said, tried to attack the Speaker, damage House property and disrupted proceedings.
The Speaker then announced suspension of the three CPI-M MLAs -- Nazmul Haq, Sushanta Besra and Amjad Hossain for unruly behaviour.
Annoyed with the Speaker's decision, Left MLAs rushed to the well as also Trinamool members.
The CPI-M claimed that some TMC members physically assaulted party MLA Debolina Hembrom by dragging her by the hair.
The Opposition Congress till recently in the treasury bench sat quietly during the uproar.
The Speaker continued with the normal business of the house and discussion took place on West Bengal Scheduled Caste and Scheduled Tribe (Identification) Amendment Bill, 2012.
Congress members, who did not participate in the discussion, walked out of the House in protest against the violence.
The Left MLAs also walked out protesting against the suspension of the three MLAs.
Left Front members led by the Leader of the Opposition went on a dharna in the assembly lounge shouting anti-government slogans.
"The suspension of the three members is against the principles of natural justice and the constitution because they were not given an opportunity to be heard. They have been punished without being able to defend themselves," Mishra said.
Parliamentary Affairs Minister Partha Chatterjee rejected this saying "Under Section 347 the Speaker may direct any member whose conduct is objectionable to withdraw from the House."
Left members, later, met Governor M K Narayanan at Raj Bhavan.
CLP leader Mohammad Shorab also led a delegation to the governor expressing shock at the unruly incidents and seeking his intervention.