An al-Jazeera cameraman detained by American forces in Afghanistan was last night released after spending nearly six years imprisoned without charge at Guantánamo Bay.

Sami al-Haj, 39, was arrested on the border between Pakistan and Afghanistan on December 15 2001, while on assignment to cover the war against the Taliban. Although he had a valid visa to work in Afghanistan, US intelligence alleged that he was an al-Qaida operative, and he was transferred to Guantánamo in June 2002.

Last night, his lawyer, Clive Stafford Smith, said Haj was en route to his home in Sudan to be reunited with his wife and son. He said: "I'm very glad Sami has finally been released, but the question is why he wasn't freed many years ago."

The US military alleged that Haj had secretly interviewed Osama bin Laden, smuggled guns for al-Qaida and worked as a financial courier for Chechen rebels. But the evidence against him was never revealed, and he was never charged.

Prior to his release, Haj had been on hunger strike since January 2007, and was forced to undergo "assisted feeding" via a tube through his nose. According to Stafford Smith, he was suicidal and had throat cancer, but camp authorities withheld medical treatment. "We are very concerned about him, because he has been under a tremendous amount of stress and has been on hunger strike for 480 days. He has asked to be taken straight to a hospital in Khartoum," Stafford Smith said.

In exchange for Haj's release, the Sudanese government has agreed to ban him from working as a journalist or leaving Sudan, according to Reporters Without Borders.

Robert Ménard, secretary general of Reporters Without Borders, said: "Sami al-Haj should never have been held so long. US authorities never proved that he had been involved in any criminal activity."

Haj's case was one of number involving journalists captured by US forces while reporting from war zones. Two weeks ago US forces in Iraq released Bilal Hussein, a photographer from the Associated Press news agency, who was detained in Ramadi in April 2006.

Commentators in the Middle East viewed Haj's imprisonment as a proxy punishment for al-Jazeera, whose broadcasts have angered US officials.

When the BBC reporter Alan Johnston was kidnapped in Gaza, Haj appealed for his release. Johnston in turn, called on the US authorities to free Haj. But Stafford Smith said much of the western media had been slow to take up Haj's case.

A spokesman for the Pentagon refused to comment on the case.