An alert has been sounded across Bihar after the February 13 German Bakery blast in Pune and attack by Maoist guerrillas on joint forces camp in West Bengal. A senior police official said today that security has been tightened at Patna Airport, railway stations, bus stands and all important religious places after taking serious note of these incidents. ADG (headquarters) U S Dutt said that all the security personnel have been asked to keep a close watch on the anti-social elements. Meanwhile, the police headquarters cancelled the leave of its personnel till February 26.