NEW DELHI, Oct. 25 (Xinhua) -- India's federal government issued an advisory asking states to ensure safety and security of journalists working in the country, an official said Wednesday.

The directive issued by Indian home ministry said all cases of attacks on journalists should be investigated promptly to ensure that criminals responsible are booked in a time bound manner.

"Fourth Estate is an important institution of the democracy. It ensures that citizens are able to express their opinions freely without any fear and coercion as provided under the Constitution of India," reads the advisory.

"It is the duty of the state to ensure safety and security of the journalists who ensure that the Fourth Estate discharges this key duty."

The federal government's missive was issued in backdrop of the last month's killing of two journalists, Gauri Lankesh in Bengaluru and Shantanu Bhowmick in Agartala.

Lankesh, a senior Indian journalist and an outspoken activist, was shot dead outside her residence in southwestern state of Karnataka, while as Bhowmick was hacked to death by mob in India's northeastern state of Tripura while covering a protest.