Mumbai, July 10 (IANS):  Security was beefed up at several key stations here Friday following intelligence alerts of a probable attack on the eve of the third anniversary of the 7/11 terror blasts.

"Security measures were intensified Thursday at Churchgate, the Western Railway headquarters and Andheri," a railway official told IANS on condition of anonymity.

Traffic on certain approach routes to Andheri and Churchgate was diverted and random checks, machine checks, frisking and checking of vehicles were being carried out by personnel of the Mumbai Police, Railway Protection Force (RPF) and the Government Railway Police (GRP).

The network of suburban trains, encompassing services by the Central Railway, Western Railway and Harbour Line, is the lifeline of Mumbai and is used by over seven million commuters daily.

On July 11, 2006, seven powerful bombs ripped through suburban trains, leaving 209 people dead and over 700 injured.

The attack was carried out by the Lashkar-e-Taiba and the banned Students Islamic Movement of India (SIMI). Detailed investigations also pointed at the involvement of the Indian Mujahideen (IM).

Pressure cookers with a 2.5 kg deadly concoction of RDX, ammonium citrate and other chemicals were placed in the first class men's compartments of suburban trains of the Western Railway during the evening peak hours.

The blasts were triggered within 11 minutes at or near Matunga Road, Mahim, Bandra, Khar Road, Jogeshwari, Borivali and Bhayander suburban railway stations, catching commuters returning home from work.