New Delhi, May 23 (IANS) Expressing his sympathy for the lives lost in the terror attack at a naval base in Pakistan's port city Karachi, Home Minister P. Chidambaram Monday said India had to remain constantly on the vigil due to the happenings in its troubled neighbourhood.

 
 “I have described our neighbourhood as a troubled neighbourhood. So we have to remain constantly on vigil. We are not happy about the incidents happening in Pakistan. We are sorry that lives are lost. But, that is today a troubled state,” home minister told reporters here.
 
 The terror siege on a naval base in Karachi ended Monday afternoon after nearly 16 hours, leaving at least 12 security personnel and four attackers dead.
 
 He added that any incidence of terrorism in the region must be viewed “very gravely and we must increase our vigil”.
 
 “We remain alert and we have alerted states based on whatever intelligence we have,” added Chidambaram.
 
 On reports of Taliban supremo Mullah Omar being dead, he said there were “contradictory reports”.
 
 “But, today Afghan authorities have disclosed that he was killed. We have to see if it is true or not,” said the minister.