Prime Minister Abhisit Vejjajiva called off a one-day trip to Vietnam for a Southeast Asian leaders summit as tension remained high, with tens of thousands of protesters defying orders to end a six-day siege of Bangkok’s main shopping district.

Despite the decree, the red-shirted supporters of ousted former Prime Minister Thaksin Shinawatra promised their biggest rally yet on Friday after briefly storming parliament this week.

Nearly 1,000 protesters tried to push through anti-riot forces guarding Thaicom Pcl’s satellite earth station in northern Pathum Thani Province.