Two more saw mill labourers were killed and four others injured by Dima Halam Daodah (DHD)-Jewel faction militants during an overnight raid in central Assam's North Cachar Hills district, official sources said on Wednesday.

With this, the toll of saw mill workers killed by the DHD(J) ultras, also known as 'Black Widows', since last evening has risen to 10, sources said.

The ultras burnt down four saw mills at Langri, under Doyungmukh police station, at around 11 pm, gunned down two labourers there and wounded four others, the sources said.

Two of the critically injured were shifted to the Gauhati Medical College Hospital, the sources said.

Prior to this killing, the insurgents had set ablaze two saw mills at Bithor village and shot dead eight workers and injured two others on Tuesday.

In both the incidents, the extremists first set the saw mills ablaze and then made the workers stand in a row before indiscriminately firing them, the sources said.

The workers were from different communities like Karbi, Nepali, Bengali and Assamese, the sources added.

The motive behind the killing was stated to be the saw mill owner's failure to pay heed to DHD(J) warning to shut down their business and not cut trees so as to preserve the forests.

The attacks took place a day after the peaceful first phase of polling to the Autonomous Council of Norch Cachar Hills District in which an estimated 80 per cent votes were cast.

The victims of the first incident were identified as R C Ingti, Jaan Timung, Deben Soren, Manoj Das, Babul Das, Dilip Soren, Hasam Das and Jungbahadur Chetri.