The M-79 grenades involved in a series of bomb blasts in Bangkok Thursday night were fired from the rally area of "red-shirts" protesters, Suthep Thaugsuban, deputy Prime Minister for security affairs said.

Suthep, who heads the Centre for the Resolutions of Emergency Situations or CRES said in a televised address around 11:30 p.m. that the grenades were fired from behind the King Rama VI statue where the "red-shirt" protesters were demonstrating.

The blasts hit at least four sites of Silom area, leaving at least one dead and 75 injured, hospitals said.

He warned residents in the area to stay away more than 400 meters from the main road as the grenades have a range of 400 meters.

It is not convenient for police and troops to enter the rally site to handle the emergency at night, he said.

Prime Minister Abhisit Vejjajiva, Defense Minister Prawit Wongsuwan and Army Commander Anupong Paojinda are trying to return the situation to normal.

On Thursday evening, the Civil Court issued an injunction against the use of force to break up the "red-shirt" rally at the Rajprasong Intersection.

But the court noted that the demonstration affected the public so the government could use internationally-accepted measures to deal with the protesters from lighter to harsher measures.