BANGKOK - Thailand's pro-establishment "yellow shirts" activists demanded military action against anti-government "red shirt" protesters on Thursday and an end to "anarchy" in the capital, a day after clashes turned a busy expressway into a deadly battle zone.

The re-emergence of the "yellow shirts" - best known for shutting Bangkok's airports for a week in 2008 - added to the volatility on the streets of the Thai capital, where a seven-week standoff has killed at least 27 people and wounded nearly 1,000.

The "yellow shirts" draw their support from Thailand's business and bureaucratic elite, whose pervasive influence is deeply resented by the "red shirts" - mostly from the rural and urban poor, who make up the vast majority of the country's more than 60 million people and revere populist former Prime Minister Thaksin Shinawatra, who was ousted in a 2006 military coup.