Reporting from Bangkok, Thailand, and Phnom Penh, Cambodia -- Anti-government demonstrators and Thai troops battled in the streets of Bangkok on Saturday in a conflagration of grenades, gasoline bombs and rubber bullets, leaving 18 people dead and more than 650 wounded.
Five soldiers and 13 civilians, including a Japanese journalist, were killed, the Associated Press reported.
As protests that have dragged on for a month sharply escalated, hundreds of the demonstrators also forced their way into government offices in two northern cities, raising the stakes for Prime Minister Abhisit Vejjajiva and his military-backed government.
"The situation at the moment is so confused," said Pranee Thiparat, a political science professor at Bangkok's Chulalongkorn University. "Anarchy rules Bangkok!"
In a televised address, Abhisit vowed to restore calm.
"The government and I are still responsible for easing the situation and trying to bring peace and order to the country," he said.
The "Red Shirt" protesters, mostly drawn from rural and working-class communities, are demanding that Abhisit dissolve parliament, step down and hold a general election.
The demonstrators, many of whom support former Prime Minister Thaksin Shinawatra, want an end to what they see as entrenched rule by the rich and powerful. Thaksin, a billionaire, was ousted in a 2006 coup, charged by military officials with corruption and abuse.
As the riots spread Saturday night toward an area popular with backpackers, the army pulled back to Bangkok's old quarter and called for a truce.
"If this continues, if the army responds to the Red Shirts, violence will expand," army spokesman Sansern Kaewkamnerd said.
But protesters raised the ante, calling on Abhisit to leave the country immediately. They also displayed a protester's corpse draped in a Thai flag, and held up pictures of several others, prompting cries of anger and weeping from the crowd.
Several soldiers who had been relieved of their weapons were marched onto a stage Saturday night. Protest leader Nattawut Saikua urged followers to detain more soldiers but to avoid hurting them, even as he blamed Abhisit for the deaths.
"This has resulted from the prime minister's refusal to step down," Nattawut said, referring to the dead protester. "This is Thai society's most serious loss."
Demonstrators believe that Abhisit, who came to power in a 2008 parlia- mentary vote, lacks a popular mandate.
With their demands unmet and the prime minister ostensibly willing to consider an election in a few months, the Red Shirts had risked seeing momentum dwindle among their hard-core supporters, said Don Pathan, a columnist for the Nation newspaper.
"It's definitely an escalation," he said.
Before Saturday's riots, police and soldiers, many from working-class backgrounds similar to the protesters', hadn't used deadly force.
A number of police officers expressed sympathy, some by hugging protesters, shaking hands and even waving Red Shirt paraphernalia.
Some analysts, meanwhile, said the unrest could prompt the military to step in, as it has several times before.
"There might be a coup," Chulalongkorn University's Thiparat said. "There's a real split both in the military and police forces, a serious one. That partly explains why the Abhisit government hasn't really been able to enforce law and order during the past three weeks."