By Subir Bhaumik BBC correspondent in Calcutta

During the past few days, separatist rebels have kidnapped two officers of the state's public works department, four government contractors and two of their drivers.

Officials say the rebels are targeting the state's administration in the hill areas of the state.

They are hoping that the administration in these areas collapses as a result.

Police said armed separatists kidnapped Suranjan Das, an officer of the public works department in Khowai sub-division of Tripura's West District, after stopping his vehicle at Mongkabari late on Monday.

Two government contractors accompanying Mr Das and their driver were also kidnapped.

On Sunday, another officer of the public works department was kidnapped in Kanchanpur in North Tripura district, along with two government contractors and their driver.

In both cases, the officials had gone to inspect work on two bridges by the contractors.

Rebel violence

The outlawed National Liberation Front of Tripura (NLFT) has been blamed by the police for these incidents.

The NLFT, they say, is upset with the landslide victory of the ruling Communists in Tripura's state assembly elections in February.

Since they, they have unleashed a wave of violence against Bengali settlers, government officials and security forces, killing more than 50 people and kidnapping as many.