Culling operations began in Tripura's bird flu-hit border district of Dhalai on Tuesday morning with authorities setting a target of killing more than 25,000 chicken.

The culling operations would continue for the next three days at Mohanpur and seven village panchayat areas of Kamalpur sub-division of the district, where about 3,000 chicken had died during the past fortnight, official sources in Agartala said.

A team of doctors from the National Institute of Communicable Disease have reached the spot and villagers were cooperating with the rapid response teams.

Measures are in place to control the spread of the disease and an isolation wing was opened at Kamalpur hospital to treat any case of infection.

An alert has been sounded across the state prohibiting import of poultry, including from neighbouring Bangladesh with which the state shares a 856 km-long border.

The Border Security Force has sealed the border and is maintaining a strict vigil so that no poultry from outside enters the state.

The avian virus was found in samples of dead chicken sent from the area to High Security Animal Disease Diagnostic Laboratory in Bhopal.