Calling for tighter security vigil in IHK, Indian Prime Minister Manmohan Singh on Friday warned that terrorists were waiting in camps across the border to infiltrate into the state. "There are reports of a large number of terrorists waiting in camps across the border and attempts to infiltrate into Jammu and Kashmir are increasing. Cross-border terror camps are being reactivated, Singh said. He, however, did not name Pakistan. "We need to be ever vigilant if infiltration attempts are to be foiled and security maintained," he added. Addressing the all-India conference of director generals and inspector generals of police in New Delhi, Singh said the security situation in the state had witnessed "a gradual, yet substantial" improvement in the recent months. The Prime Minister described the recent Mumbai and Delhi blasts as a "grave reminder" of the great challenge that terrorists posed to India's national security. "The national security situation continues to be uncertain. Recent terror attacks in Mumbai and Delhi are a grave reminder to great challenge posed by terrorists to our nation's security," Singh said after distributing the police meritorious service medals to officers. He also noted that left-wing extremism had also claimed lives of many innocent people and policemen. The Mumbai blast took place July 13 and the Delhi blast outside the high court premises Sep 7, both claiming many lives and injuring many more.