Guwahati/Nagaon: Fifteen people have been arrested overnight for the lynching of two young sightseers in Assam's Karbi Anglong district on Friday, 10 more for allegedly spreading hate messages and a teenaged boy over "fake news" about child kidnappers on Facebook.

The arrests came amid violent protests against the lynchings - which were triggered apparently by suspicion that the duo were child kidnapers - in various parts of the state and the "exodus" of Karbi Anglong natives from neighbouring Nagaon district, fearing attacks.

Police rounded up 11 members and supporters of the Congress student wing, National Students' Union of India, in Nagaon town after they allegedly tried to attack people from Karbi Anglong on Saturday at bus stands and markets. One of them was later arrested, officers said.

Dibrugarh police arrested a man, Simanta Terang, for allegedly posting hate messages on social media, and nine others were arrested on similar charges from other districts.

Seventeen people, including seven policemen, were injured in Guwahati on Sunday as a march by 2,000 people protesting the lynchings erupted in violence.

A mob of 200 to 250 people in Panijuri village had allegedly beaten to death Nilotpal Das, 29, and Abhijit Nath, 30, who had arrived from Guwahati to see a nearby waterfall, on Friday night.

Officers have blamed the killings on "fake news" circulating across social media for the past few days about child kidnappers from outside Assam being on the prowl across the state.

Bhupendra Terang, 18, a resident of district headquarters Diphu, was arrested on Saturday night and booked under the IT Act for allegedly posting false information on Facebook about child kidnappers.

Five people were arrested over the lynching on Saturday, and 10 more on Sunday. All are aged between 18 and 49.

"A few more people involved in the lynching have been identified but they are in hiding. We are searching for them," Assam director-general of police Kuladhar Saikia said.

"Two cases have been registered so far, one for the murder and the other for sharing a video of the incident and fake news."

Saikia said a cell headed by additional director-general of police Harmeet Singh would take steps to improve the police's capacity to monitor social media and prevent its misuse.

In Guwahati, a protest by 2,000 marchers seeking justice for the two lynched youths erupted in stone-throwing, the police said. "Seven of our personnel were injured in stone-throwing and we had to resort to a baton charge," deputy commissioner of police (central) Ranjan Bhuyan said.

Khanindra Talukdar, who was part of the march, said 10 protesters, including three girls, were injured in police caning.

Biman Sarma, a senior citizen who had joined the march, accused the police of caning the protesters without provocation. But fellow protester Jabes Alam said some of the marchers had indeed stoned the police. Three youths have been picked up for interrogation.

Finger at BJP

A forum against superstitious beliefs on Sunday alleged the BJP-led government in Assam was promoting superstition and the lynchings were a fallout of it.

It said rumours that some sinister pisol manuh (slippery men) and witches were stealing children had not just prepared the ground for the lynchings but led to the harassment of many other innocent people.

"Superstitious beliefs are being spread under the patronage of the state government," said Chandramohan Sarma, president of the Ellora Vigyan Mancha.

"There have been numerous instances of ministers to top bureaucrats spreading such beliefs. The state government has been promoting vaastu shastra, astrology and unscientific activities like worshipping rivers through Namami festivals."

The Krishak Mukti Sangram Samiti said that a "communal political" party was spreading rumours to destabilise the state before the publication of the final draft of the National Register of Citizens.

Protesters in Guwahati demanded the dismissal of Karbi Anglong deputy commissioner Mridul Kumar Mahanta for his "irresponsible comment" that the lynched duo should have gone to the area with permission from the district administration.