HANOI, Vietnam - A writer for one of Vietnam's most popular news websites has been arrested, her editor said Tuesday, as police continued to crack down on journalists and bloggers who have run afoul of the communist authorities.

Doan Trang was arrested Friday, said Nguyen Anh Tuan, the editor-in-chief of VietnamNet.

"I was informed that her arrest was for activities outside of VietnamNet," Tuan said.

Police in Hanoi declined to comment.

Trang, 31, wrote stories about sensitive territorial disputes between China and Vietnam, who both claim sovereignty over the Spratly and Paracel islands in the South China Sea.

Access to most of her articles on that and other topics was blocked on Tuesday.

Vietnam's government has been sensitive about criticism of its handling of relations with China, its much larger northern neighbour, as well as plans by a Chinese firm to build a large bauxite-mining operation in the Central Highlands.

Critics say the project will cause serious environmental damage and could give the Chinese access to the strategically important region along Vietnam's border with Laos.

Trang was arrested one day after authorities detained 37-year-old blogger Bui Thanh Hieu, who has been critical of the Communist Party's handling of relations with China and land disputes with the Roman Catholic Church.

Last week, one of Vietnam's most popular bloggers, Huy Duc, was fired by the Saigon Thiep Thi newspaper after the Communist Party complained about writings on his blog, "Osin."

The government tightened its rules for bloggers earlier this year, saying they must restrict their writings to personal matters.