Three days after steering Trinamool Congress to a landslide victory in West Bengal assembly elections, Mamata Banerjee was sworn in as Chief Minister of the state for the third consecutive term today and vowed to not "spare" those behind political violence sweeping the state post-poll results.

Governor Jagdeep Dhankhar administered the oath to 66-year-old Mamata at a low-key ceremony in the "Throne" room of the British colonial era building Raj Bhavan, with Covid-19 protocols in place.

Apart from senior TMC leaders like its Secretary General Partha Chatterjee and Subrata Mukherjee, Mamata's poll strategist Prashant Kishor and her lawmaker-nephew Abhishek Banerjee were present at the swearing-in ceremony.

Leaders of opposition parties including the BJP, the Left and the Congress did not attend the ceremony, reports our New Delhi correspondent.

Mamata took the oath in Bangla, quite natural for a person whose main plank was Bengali sub-nationalism to resist the Hindutva narrative of BJP.

Mamata alone took oath today and her cabinet will be expanded with the induction of other ministers on May 9, the birth anniversary of Nobel laureate Rabindranath Tagore, TMC sources said.

The oath-taking ceremony was held even as the BJP, which has emerged as the main opposition party in the state with 77 seats, held a protest at nearby Hastings office against attacks on its workers allegedly by TMC since Sunday night.

The saffron party has claimed that several of its workers were killed and party offices were set on fire and vandalised. Party president JP Nadda and state unit chief Dilip Ghosh were present at the protest.

Referring to incidents of violence post-election results, Mamata said, "I will tackle law and order from today and deal with these sternly. This is my second priority."

"We will not spare anyone (perpetrators of violence), and will do everything to restore law and order," she told journalists after taking oath. She urged all political parties to help maintain peace and order.

Congratulating Banerjee on assuming office for a third time, Dhankhar expressed the hope and expectation that she will govern the state according to the constitution and rule of law.

"Our first priority is to end the horrendous and senseless violence that has affected society at large. Post-poll violence, if it is retributive, is antithetical to democracy," said Dhankhar who had been at loggerhead with the Mamata government over the violence and has had a running feud with Banerjee on several issues.

Mamata, for her part, said she has taken charge "just now" and some political parties were indulging in atrocities in places where they won.

While the BJP has accused the TMC of targeted attacks against its workers and vandalisation of its offices, the ruling party has also claimed that its supporters were attacked and killed at places where the saffron party won.

Addressing the protest rally at Hastings, JP Nadda vowed to protect democracy and save the people of West Bengal from the "vicious cycle of political violence."

"I am going to districts like North 24 Parganas to be by the side of our members who were at the receiving end of brutal violence not witnessed in independent India. We want to tell the entire country about this," said Nadda who had come under attack during campaign in the district in February.