ISLAMABAD: A fifth Pakistani rights activist has gone missing, his colleagues said Thursday, as the United Nations raised concerns over shrinking freedoms for campaigners.

Samar Abbas, a middle-aged IT worker and head of the anti-militancy Civil Progressive Alliance, disappeared under mysterious circumstances after arriving in the capital Islamabad from Karachi on Saturday, January 7, according to Talib Raza, a colleague from his organisation.

"We formed the alliance to protect the rights of minorities. He had launched a struggle against the banned militant outfits' activities and we together staged protests for the rights of the minorities," said Raza.

"This seems to be an organised attempt to shut the progressive and liberal voices in the country," he added.

Four leftist bloggers were previously reported missing from various cities between January 4 and 7, raising fears of a crackdown on social media, the last bastion of free speech in a country where journalism is increasingly under threat.

Human Rights Watch said their near simultaneous disappearances raised concerns of government involvement.

The government has denied this, and on Tuesday Interior Minister Chaudhry Nisar Ali Khan told the Senate authorities would soon recover all the missing.-AFP