The Thai embassy has reportedly been destroyed, as well as the Thai-owned Royal Phnom Penh Hotel.
It is believed the riots were touched off after a Thai actress said that the Angkor Wat temple – the national and international symbol of Cambodia – belonged to Thailand. The actress has denied the accusation.
"This violence is very regrettable and is a tremendous loss for our nation and our people," Cambodian Premier Hun Sen said in a statement.
Phnom Penh wreckage
"These events that have occurred have been caused by a small group of people who are extremists, who incited people with lies about the Cambodian embassy in Bangkok being destroyed."
But even as he appealed for calm, gangs of youths on motorcycles started a fresh round of demonstrations on Thursday.
Thai Prime Minister Thaksin Shinawatra has recalled the Thai ambassador and said the Cambodian ambassador would be asked to leave Bangkok.
About 600 Thais made a desperate dash for Phnom Penh airport in the the dead of night after mobs of nationalist youths torched the embassy before embarking on a burning and looting spree targeting any business with Thai associations.
Five giant Thai military C-130 aircraft evacuated hundreds of people from the Cambodian capital.
