By Subir Bhaumik
BBC News, Guwahati
Twelve people have died in intensified violence in India's north-eastern state of Assam in the run-up to the second phase of general elections on Thursday.
Five policemen and their civilian driver died when rebels of the separatist Black Widow faction fired on a convoy of trucks.
The attack took place between the towns of Umrangshu and Lanka in the North Cachar Hills district late on Monday.
The faction is one of a number fighting for autonomy in Assam.
The Black Widows want an independent homeland for the Dimasa tribe.
Also on Monday, army soldiers encircled a group of insurgents at Khanamukh village in Assam's Sonitpur district on the northern banks of the river Brahmaputra and killed five rebels.
Three of those killed belonged to the hardline faction of the National Democratic Front of Bodoland (NDFB) while two were from the Muslim United Liberation Tigers of Assam (Multa).
Military spokesman Col Rajesh Kalia told the BBC that the rebels were planning to attack polling booths and kidnap a local businessman when they were encircled by troops with the help of local police.
One political activist of a Bodo political party was beaten to death by supporters of another Bodo party in western Assam's Udalguri district late on Monday.
Twenty three others were injured in that clash.
Assam police chief GM Srivastava said that security had been tightened for Thursday's polls in 11 of the 14 parliamentary constituencies in the state.
Polls in the three other constituencies in Assam were held on 16 April.