Whatsapp, an instant messaging service for smart phones, said in April that nearly one-tenth of its 500 million users were in India, making the country its largest market. The services continues to grow in India. Showing uncharacteristic agility, several government departments have started using the application to reach out to their constituents.

Here's what they're doing.

Delhi police
The Delhi police launched a 24x7 Whatsapp helpline on August 6 where the public can post details about corrupt policemen. People can record audio or video clips and send them to the helpline via the chat engine.

When people register a complaint, the police will call them back to get more information and then send the clip to a forensic science laboratory to verify its authenticity. If it is deemed authentic, the police will register a complaint and suspend the guilty policeman.

In less than a week, it has received more than 50 complaints and three policemen have been suspended.

Kochi, Chandigarh traffic police
The Chandigarh police joined WhatsApp on July 15. Within a day, they had received 300 messages and nine pictures from complainants. This allowed them to issue fines against two vehicles, according to The Times of India.

Similarly, after the success of their Facebook page, the Kochi police started a service in April called the "Whatsapp in Traffic". It lets users send in traffic complaints via text or video.  The department hopes to eventually be able to give users information about traffic jams and accidents.

Bhopal rail division
The authorities of this division launched a Whatsapp account on August 5 inviting complaints and suggestions from passengers about problems they face at train stations and on trains. The Hindustan Times reports that within four days, the division received more than 3,700 messages. But this experiment also highlighted the problems of such an open invitation. Many of these messages were in poor taste, with unsavoury jokes.

The prime minister
The Bharatiya Janata Party has set up an MPs' group on Whatsapp, headed by  Venkaiah Naidu, the urban development, housing and parliamentary affairs minister, to tackle the problem of absenteeism. All its MPs will be informed of meetings and sessions on this group. This is in line with the BJP's major social media push in recent months.

Kerala excise department
The Kerala excise department said last month it planned to use social media, including Whatsapp, to communicate the message of a campaign against liquor abuse and drug use. The campaign, called "No to alcohol, no to drugs" calls for youngster to instead become "addicted to life".