After Thursday's terrorist attack on London's transport system that claimed 37 lives and left over 700 injured, India has sounded a high alert all over the country and asked the police and paramilitary forces to step up vigil.

Minister of State for Home Affairs Sri Prakash Jaiswal said instructions have been issued and the government is determined to fight the menace of terrorism.

• Al Qaeda again: B Raman

"We have asked all the state police forces to guard religious and historical places. Just as our valiant men killed all the terrorists who dared to attack Ayodhya on Tuesday, we are confident police forces all over the country will foil any such attempt made by terrorists," he said.

According to sources, Delhi Police Commissioner Dr K K Paul has been asked to make special arrangements to protect the capital's newfound heritage Delhi Metro. Special checks are being carried out on all the national highways and major metropolitan cities to foil attempts by the terrorists to sneak in."