A prominent journalist has been interrogated in Vietnam in what human rights activists say is part of a growing campaign of harassment of writers and dissidents.

Nguyen Vu Binh, who has written several articles criticising the communist government and calling for reform, is now required to report daily for questioning by security police.

The New York-based Committee to Protect Journalists, or CPJ, says the writer was taken from his home by police on Friday and is believed to have been held in detention somewhere in the capital, Hanoi.

Nguyen Vu Binh: Needs to report to police daily

Citing information from a California-based organisation, the Democracy Club of Vietnam, the CPJ says Nguyen Vu Binh was detained on Friday as the country's newly elected parliament was meeting.

It says material was taken from his computer.

Vietnam's Foreign Ministry spokeswoman Phan Thuy Thanh denied Binh had been arrested, as earlier claimed.

"The Vietnamese authorities have neither arrested nor detained Nguyen Vu Binh," she told the BBC.

However, she said Binh had been summoned by local police to answer questions over "activities harming public order and public security".

From Party to opposition

Mr Binh formerly worked on the Communist Party's official journal.

He clashed with the authorities last year when he left his job and tried to set up an opposition party.

He was among a group of dissidents detained last September in a crackdown which surprised many observers given that it coincided with the installation of a new Communist Party chief, Nong Duc Manh, widely thought to have some reformist credentials.

It is not clear whether Mr Binh has been charged with any new crimes.

BBC interview

The Democracy Club statement says he is among a group of dissidents who wrote to the Communist leaders early in July calling for political reforms and the release of political prisoners.

Diplomats say none of the others in the group appears to have been sanctioned.

Vietnam's constitution guarantees a free press

Mr Binh had also taken part in a recent BBC interview series featuring prominent dissidents.

Despite Vietnam's constitutional guarantees of a free press, in reality dissidents take considerable risks if they speak out.

Vietnam is under constant pressure from some quarters of the international community to address allegations of human rights violations.

Much of the dialogue is pursued quietly, unlike the demands for Vietnam to root out corruption in business or streamline its inefficient bureaucracy.

The CPJ says Mr Binh's arrest violates national and international laws and has demanded his immediate release.