NEW DELHI: Worried about the vulnerability of vital installations, which was exposed after terrorists sneaked into Pathankot air base, Prime Minister Narendra Modi has asked defence authorities to ensure that all bases near the border are made into “impregnable fortresses,” although he expressed satisfaction at the way the crisis was handled.Modi, who visited the Pathankot facility on Saturday, is said to have been briefed on how India’s security forces thwarted attempts by the six terrorists to storm the technical area where vital and strategic assets were located. The attackers had positioned themselves at different locations inside the air base in an apparent effort to hoodwink the security forces and gain entry into the technical area.“Noted with satisfaction the decision-making & its execution, the considerations that went into our tactical response: PM,” the Prime Minister’s Office tweeted after Modi was briefed. Commandos from the elite National Security Guard had been called in to handle any potential hostage situation at the air base, which housed hundreds of families and 23 foreign trainees from four nations, Modi was told. Although Modi was satisfied with the operations, he asked pointed questions about how the terrorists could have entered the vital installation.Officials told ET that the PM impressed upon the air force and army to immediately take all steps to make defence bases near the border into “impregnable fortresses,” including the installation of modern electronic perimeter intrusion protection systems – as done at major airports – CCTVs and proper flood-lighting and control centres to live-monitor the boundaries of these bases.The Pathankot base and other army and IAF bases near the border do not have CCTVs or perimeter intrusion alert systems. Pathankot air base has a CCTV only at the main entry. “There can be no excuses and we have to shore up our defences to ensure terrorists are not able to infiltrate into India in the first place and our vital installations are safe from such intrusions as a back-up measure,” an official told ET.