At a press conference on Sunday afternoon, Natthawut Saikua, a red-shirts leader, said that the protesters would move to rally outside the barrack if the prime minister does not respond to the ultimatum by 9 a.m. Monday. He said the rally had attracted as many as 300,000 supporters from all over the country by then.

The first group of red-shirted protestors riding motorcycles arrived at the military compound at 10 a.m. Monday, as more red- shirts followed them and protested there until 2 p.m. when they began to return to the main rally site, Phan Fah Bridge at downtown Bangkok.

According to local media, a military source confirmed that the Army has brought an additional 20 companies of troops to the infantry regiment to protect government leaders and military commanders.

Meanwhile, Public Health Ministry Monday morning upgraded emergency service to the highest level in wake of the red-shirted protestors' arrival at the 11th Infantry Regiment compound.

The ministry prepared extra beds, blood and ambulances in case of emergency, according to Bangkok Post online.

The upgrading was announced after it evaluated that the number of protestors in Bangkok exceeds 50,000, as countless pro-Thaksin (Thailand's former prime minister) red-shirts had swarmed to the capital city since Friday to join the mass rally aiming to oust the Abhisit administration.

Although both government and sides insist all the time they will keep restrained and try to avoid violence, four explosions were heard in the afternoon from the 1st Infantry Regiment compound in Bangkok and injured two soldiers.

The Army spokesman Sansern Kaewkamnerd, speaking in an interview later with a television station, said six M79 grenade rounds were fired into the First Infantry Regiment compound at around 1:30 p.m. and the grenades were believed to have been launched from a pick-up on the overhead tollway. Two of the six rounds failed to explode.

He said one soldier had his stomach injured, another soldier's arm got wounded, and both of them had been admitted into hospital.

Hours later a suspect of this incident was arrested by police and an investigation is believed underway.

Police said the man was arrested at a checkpoint following tip- off by witnesses, without disclosing the identity of the suspect or other details.

The red-shirts leaders denied their connection with the attack.

They did admit, however, that they would take measures to further pressure the government on Tuesday, including scattering 1 million cc blood of the protestors around the Government House.

One of the leader Nattawut said that the blood will be taken from 100,000 protesters, including the red-shirts leaders, and will be scattered around the Government House at 8 a.m. Tuesday.

This will be a symbolic action, making the cabinet ministers have to walk over the protestors' blood when they enter the Government House to work, he said.

If the government still fails to dissolve the parliament after that, another million cc of blood will be poured at the Democrat Party headquarters, Natthawut added.

If it does not work, a third million CC of blood will be scattered around Abhisit's house, he said.

The red-shirts have contacted five hospitals for medical staff and equipment to help take blood donations, which will start tonight, another red-shirts leader Arisman Pongruangrong said.