BANGKOK – Thai Prime Minister Abhisit Vejjajiva on Saturday a rejected a new, compromise offer by anti-government red-shirt demonstrators to end weeks of increasingly violent protests in return for early polls. The red-shirted supporters of ousted former premier Thaksin Shinawatra immediately removed their offer to end a three-week occupation of Bangkok's ritzy shopping area if the government dissolved parliament and announced elections in 30 days. Abhisit said the peace overture looked insincere and designed only to improve the protesters' image. "They keep saying they will escalate the situation. That's why the government cannot consider the proposal," he told reporters. The mostly rural and working-class red-shirts responded by threatening more aggressive measures, including laying siege to Central World, the second-largest shopping complex in Southeast Asia, next to the stage at their main protest site. "If you want Central World shopping mall back safely, you must withdraw army forces out of the nearby Rajaprasong area immediately," a protest leader Jatuporn Prompan told supporters. The shopping center has been closed since the protesters occupied the area on April 3. The risk of violence remains high after a series of grenade blasts that killed one person and wounded 88 on Thursday in Bangkok's business district, an attack the government blamed on the red-shirts, who deny they were responsible. As part of their demands, the red-shirts also want an independent probe into an April 10 clash between protesters and the army that killed 25 people and wounded more than 800 in Thailand's worst political violence in nearly two decades. Thousands of troops, many armed with M-16 assault rifles, keep watch over red-shirts at several city intersections. Royalist pro-government protesters often gather outside their fortress-like barricade, sparking clashes in which both sides hurl bottles and insults. Jatuporn encouraged some protesters to do away with their signature red shirts to make it more difficult to separate them in the capital city of 15 million people. "We will take off our red shirt and wear other colors, but our goal and our ideals are still the same," he said. Tens of thousands of red-shirts remain encamped at the central Bangkok shopping district, vowing to stay until parliament is dissolved and defying a state of emergency that bans large gatherings of protesters. "This hardening of the battle lines between the two sides does not bode well for Bangkok's security situation and a risk of another, and this time maybe even more violent, crackdown is immediate," risk consultancy IHS Global Insight said in a note.