Three explosions shook Bangkok's business district Thursday, wounding at least four people, witnesses said, raising tensions during a showdown between thousands of troops and anti-government protesters. It was not immediately clear what caused the explosions outside the headquarters of Charoen Pokphand Group, Thailand's biggest agribusiness group, but witnesses said at least one foreigner was wounded along with a Thai woman. after the first blast. After a later fourth blast, reporters saw two more seriously injured people lying motionless. Hundreds of troops, many armed with M-16 assault rifles, have poured into the area since Monday to stop thousands of anti-government protesters from marching to the bustling district of banks, office towers and go-go bars. Not far from the explosions, tens of thousands of red-shirted supporters of former prime minister Thaksin Shinawatra have fortified their redoubt in a Bangkok commercial district with home-made barricades, expecting the army to evict them any time. Neither side shows any sign of backing down after the army's chaotic attempt to evict protesters from another site on April 10 that led to the deaths of 25 people and wounded more than 800. The army again warned it would forcibly disperse the mostly rural and urban poor red shirts who have led nearly seven weeks of protests demanding elections. “Your days are numbered,” army spokesman Sansern Kaewkamnerd said Thursday. “If you leave now, you won't be prosecuted. But if you wait until the security forces enter, you will be prosecuted. You could also be hit by stray bullets during clashes between the security forces and heavily armed terrorists.” Red Shirt leaders say another attempt to evict them would be futile. They say they will only leave Bangkok when Prime Minister Abhisit Vejjajiva announces early elections. A pro-government “multi-colored” group said it plans to gather 50,000 people for a rally at Government House in central Bangkok to voice their opposition to the red shirts, splitting the capital into opposing groups.