Indian Coast Guard is the 'central pillar' of India's coastal security architecture along with the Navy and Marine Police, Union Home Minister Rajnath Singh said here on Friday.Commissioning ICGS Sarathi, a defence vessel, into the Indian Coast Guard here, the minister said maritime terrorism continues to be a security threat as India has a long coastline with many big cities and security installations."The job of Coast Guard is extremely challenging as they are responsible for security of coastal areas as well as the territorial waters," the minister wrote on Twitter.Indian Coast Guard should also work towards the safety and conservation of India's marine ecosystem, the minister said.Speaking on the occasion, Singh said the Centre has adopted a comprehensive and integrated coastal security scheme to strengthen India's coastal security network.Oceans and seas act as natural security shields and also bring new opportunities for economic prosperity, the minister said.