India has approved four new tiger sanctuaries and a "tiger corridor" in the latest of a series of measures designed to stem the decline of the threatened species.

Prithviraj Chavan, chief minister of the western state of Maharashtra, announced the steps that will add more than 500 square kilometres (200 square miles) to the state's protected forest area.

"Many do move from one forest to another. That's why tiger corridors are crucial. These new sanctuaries will help in strengthening tiger corridors," Chavan told reporters late Thursday.

About 170-180 tigers are believed to remain in Maharashtra state.

In an effort to crack down on poaching, the state's forest minister said last month that action would not be taken against officials who fire on poachers caught hunting tigers.

India is home to half of the world's rapidly shrinking wild tiger population but has been struggling to halt the big cat's decline in the face of poachers, international smuggling networks and loss of habitat.

The country has seen its tiger population plummet from an estimated 40,000 animals in 1947, when it gained independence from British colonial rule, to just 1,706 in 2011.