Intelligence alert has been issued for 22 airports in four border cities.

Highlights Vigil at Jammu and Kashmir, Punjab, Rajasthan, Gujarat, Delhi

Agencies concerned about terror attack in retaliation for surgical strike

Today 3 Pakistan terrorists tried to target an army base in Kashmir

Intelligence agencies have warned of a possible terror attack at airports in four states as well as Delhi. 22 airports in the four states have been sent detailed warnings and authorities have confirmed high security measures are being implemented.Jammu and Kashmir, Punjab, Rajasthan and Gujarat - all border states - have, like Delhi, been marked for careful vigil. The Civil Aviation Security Bureau has also written to the police chiefs in each state, the CISF or paramilitary force which guards airports, as well as to state-run and private airlines alerting them to the security threat.While baggage will be subjected to more random and detailed checks, parking lots as well as loading areas used by airport vehicles will be more carefully monitored.A high security alert is standard for the festival season. But agencies are concerned about a terror attack in retaliation for last week's surgical strikes in Pakistan-Occupied Kashmir which saw soldiers targeting seven terrorist launch pads or gathering areas.Yesterday, National Security Advisor Ajit Doval briefed Prime Minister Narendra Modi on security at the Line of Control in Jammu and Kashmir. Intelligence agencies have warned of nearly 100 terrorists being prepped to cross the de-facto border before winter sets in and the routes into Kashmir are covered with snow.The Line of Control has been simmering with cross-border firing and violations of the ceasefire.

This morning, soldiers killed three Pakistan terrorists who tried to target an army base in the border district of Kupwara in Kashmir. Maps and arms recovered established that they were from Pakistan, said the army.The cross-border strikes carried out by India a week ago were in response to a deadly attack at an army camp in Uri in Kashmir last month, in which 19 soldiers were killed by a group of four Pakistani terrorists.