Hanoi: Thousands of Vietnamese set fire to foreign factories and rampaged in industrial zones in the south of the country in an angry reaction to Chinese oil drilling in a part of the South China Sea claimed by Vietnam, officials said. The brunt of violence, one of the worst breakdowns in Sino-Vietnamese relations since the neighbors fought a brief border war in 1979, appears to have been borne by Taiwanese firms in the zones in Binh Duong and Dong Nai provinces that were mistaken for Chinese-owned companies.