Violent protests erupted near Jamia Millia Islamia in Delhi and at the Aligarh Muslim University in Uttar Pradesh, while West Bengal plunged deeper into chaos on Sunday during the stir over the new citizenship law with incidents of arson and loot reported from the state and the northeast, acts which Prime Minister Narendra Modi alleged were being instigated by the "Congress and its friends".

An uneasy calm prevailed in Assam, epicentre of the agitation, as curfew was relaxed in Guwahati and Dibrugarh for several hours following improvement in the situation but peaceful protests were held amid calls by the Asom Gana Parishad (AGP) for resignation of its ministers.

The party, which is part of the BJP-led government in Assam, decided it will move the Supreme Court against the amendments made in the Citizenship Act.

In Assam's Guwahati, two more persons succumbed to gunshot wounds suffered in the police firing on Thursday, taking the toll to four. However, protesters claimed that five persons have died in police firing.

In the national capital, protesters torched four public buses and two police vehicles as they clashed with the police in New Friends' Colony near Jamia University during a demonstration against the amended Citizenship Act, leaving six cops and two firemen injured, officials said.

Sources said that at least 31 students were brought to a nearby hospital after the violence and 11 of them were admitted.

Soon after the violence, Jamia Millia Islamia Chief Proctor Waseem Ahmed Khan claimed that the Delhi Police entered the campus forcibly without any permission and beat up staff members and students who were forced to leave the campus.

Condemning the police action, university vice chancellor Najma Akhtar said students who were inside the library which was allegedly surrounded by the police have been taken out and are safe.

Police said they entered the university campus only to control the situation, after protesters indulged in violence.

Protests in Guwahati on Sunday, December 15. Photo credit: PTI

The university had on Saturday cancelled exams and announced vacation till January 5 in view of the tension, while the Aligarh Muslim University too was closed till January 5.

In Uttar Pradesh, hundreds of students of Aligarh Muslim University clashed with the police at a campus gate after which police used batons and teargas to disperse them.

Soon after the protest near the Jamia Millia University in Delhi, the students started gathering at the Babey Sir Syed Gate and shouted slogans against the law and police action on demonstrators in the national capital.

AMU Proctor Prof Afifullah Khan said some security personnel have been injured in brick-batting near the gate. Police said the student broke down the police cordon. Police have sealed all gates to the campus.

Students have been protesting against the law in the campus for the last few days.

Internet services were shut in West Bengal's six districts -- Malda, Uttar Dinajpur, Murshidabad, Howrah, North 24 Parganas and parts of South 24 Parganas -- as the state convulsed with violence for the third successive day despite Chief Minister Mamata Banerjee's appeal for calm.

Hitting out at the Trinamool Congress dispensation over advertisements against the NRC and the citizenship law, Governor Jagdeep Dhankhar said it is unconstitutional and a head of government can't use public money for such campaigns.

Incidents of violence, loot and arson were reported from Nadia, Birbhum, North 24 Parganas, South 24 Parganas and Howrah districts, police said.

In Amdanga area of North 24 Parganas and Nadia's Kalyani, agitators blocked thoroughfares, setting logs on fire. Shops were also ransacked and people burned tyres in Deganga in North 24 Parganas.

Train services were hit in South 24 Paraganas as protesters blocked tracks near Nungi and Akra stations, which were also ransacked.

Similar protests were reported from Domjur of Howrah district, and parts of Burdwan and Birbhum, with agitators taking out rallies and raising slogans against the Modi government.

In Malda district, protestors ransacked Bhaluka railway station and staged a road and rail blockade at Sagardighi.

The cost of damage to railway property assessed so far during the protest in Kharagpur division is over Rs 15.77 crore till Saturday, officials said.

At a poll rally in Jharkhand's Dumka, PM Modi said, "The Congress and its allies are stoking fire over the Citizenship Act, but people of northeast have rejected violence. Actions of the Congress prove that all decisions taken in Parliament are correct."

"People who are setting fire (to property) can be seen on TV... They can be identified by the clothes they are wearing," he said without elaborating.

In Assam, Gauhati Medical College and Hospital Superintendent Ramen Talukdar told PTI, "Ishwar Nayak died last night and Abdul Alim succumbed to his injuries this morning."

Two persons, identified as Sam Stafford and Dipanjal Das, were shot dead on Thursday. Police said 175 people have been arrested and 1,406 taken into preventive custody across Assam.

Special trains have been arranged to ferry stranded passengers. The West Bengal chief minister has directed officials at Coochbehar and Jalpaiguri, two districts near Assam, to ensure supply of food and water to the passengers stranded due to the blockades.

AGP leader Kumar Deepak Das said the party would file a petition in the Supreme Court for revocation of the amended Citizenship Act, even as party functionaries urged its top brass to clear their stand on the issue.

Members of the AGP's Guwahati unit also held demonstrations outside party headquarters in Ambari area, demanding resignation of three ministers, including party chief Atul Bora.

Later, at a press conference, Bora said as the legislation has already become an Act, at least the Brahmaputra valley should be excluded and it may be implemented in the Barak valley.

The Barak valley, which has a significant Bengali population, has not seen any major agitation.

AGP leader and Assam minister Keshab Mahanta said the party has not left its "old stand" of opposing the law.

"Though we are a part of the NDA, our stand has not changed. We still do not want this Act to be implemented in Assam and the northeast," he said.

The party's lone MP in Rajya Sabha, Birendra Prasad Baishya, opposed the Bill during discussion, but voted in favour of it following which the party is facing severe criticism.

Students organisations AASU and AJYCP also took out rallies across the state, seeking revocation of the law.

rude oil and gas production in Assam has been hit, affecting supply of petrol, diesel and LPG in many districts. The two major producers Oil India Ltd (OIL) and Oil and Natural Gas Corporation (ONGC) on Sunday said their gas output have totally stopped, while oil production is down by over 75 per cent.

In another northeastern state of Meghalaya, curfew was relaxed in parts of Shillong from 6 am to 7 pm on Sunday.

Banks and educational institutions remained shut with the North Eastern Hill University postponing all examinations to February 2020. Traffic was negligible on the roads during the relaxed hours of curfew and markets were shut for most parts of the day.