Guwahati: A total of 52 people, including four women, were killed and 10 others injured in a series of attacks by suspected NDFB (Songbijit) militants in Sonitpur and Kokrajhar districts of Assam.

Five attacks took place at various spots - men, women and children were mowed down with AK-47 bullets, sources in the police said.

Three more persons were believed to have been killed in Kokrajhar but police were yet to recover the bodies from the remote place.

Prime Minister Narendra Modi condemned the acts and called it as "an act of cowardice".

A spokesperson of Assam Police said 30 persons were gunned down in Sonitpur district alone, while four were killed in Kokrajhar on Tuesday evening.

"In Sonitpur district, 30 people have been killed. While 24 were gunned down in Biswanath Chariali, six were killed in Dhekiajuli," the spokesperson told PTI in Guwahati.

In Kokrajhar district, four deaths have been confirmed at Pakhiriguri, while three more are suspected to have been killed at the interior place of Ultapani, he said.

"All these people were killed in serial attacks by suspected militants of National Democratic Front of Bodoland (NDFB) (Songbijit)," the official said.

All those killed in Sonitpur attack were stated to be Adivasis, said Superintendent of Police Sanjukta Parasar.

A group of NDFB(S) militants with sophisticated arms fired at people in Sonajuli under Biswanath Chariali sub-division in Tinisuti near the Arunachal Pradesh border, she said.

In the attack, 24 persons were killed and six others injured, she said.

The incident site is located very near to the inter-state border between Assam and Arunachal Pradesh.

Six more persons were killed at Batachipur under Dhekiajuli police station and the bodies of the deceased have been recovered, Parasar said.

In Kokrajhar district, four bodies were recovered while three others were suspected to have been killed in two different attacks by NDFB(S) militants in the evening.

"The first attack took place at Pakhiriguri under Serfanguri police station in which four women were killed and

four others were injured," Kokrajhar SP Sunil Kumar said.

Three more persons are suspected to be killed in another attack by the militants of the NDFB(S) at Ultapani under Kokrajhar police station, he said.

"The place at Ultapani is very interior. The police party is reaching there to give verified facts," Kumar said.

The SP said the injured have been rushed to a hospital in Kokrajhar town from Pakhiriguri, which is in a jungle near Indo-Bhutan border.

At least three persons were seriously injured yesterday in six serial grenade blasts and firing in Kokrajhar district.

Meanwhile additional paramilitary personnel were being rushed by Union home ministry to Sonitpur and Kokrajhar districts of Assam where NDFB(S) militants shot dead 45 people tonight.

Home ministry sources said it has sought a report from the state government on the series of attacks by the militants.

They said Home Minister Rajnath Singh is constantly monitoring the situation in the places of the attacks.

Rajnath Singh spoke to Assam Chief Minister Tarun Gogoi and offered him all assistance to deal with the situation arising out of the massacre.

He asked Gogoi to firmly deal with the situation.