Manning 35
US soldier Bradley Manning has been sentenced to 35 years in jail for leaked thousands of top-secret diplomatic cables to WikiLeaks (Reuters)

Rights groups have condemned the 35-year jail sentence passed on American soldier Bradley Manning who leaked thousands of top-secret diplomatic cables to WikiLeaks.

Manning, 25, was sent to jail and dishonourably discharged from the army by a military court at Fort Meade, Maryland.

The American Civil Liberties Union (ACLU) described the sentencing as a "sad day for Bradley Manning but also a sad day for all Americans."

The Centre for Constitutional Rights was outraged. It called manning a "patriot".

Amnesty International asked President Barack Obama to set Manning free immediately.

He had already spent three years in pre-trial detention, including 11 months in conditions described by the UN Special Rapporteur on Torture as cruel and inhumane.

"Bradley Manning acted in the belief that he could spark a meaningful public debate on the costs of war and specifically on the conduct of the US military in Iraq and Afghanistan," said Widney Brown, senior director of international law and policy at Amnesty.  

"His revelations included reports on battlefield detentions and previously unseen footage of journalists and other civilians being killed in US helicopter attacks - information which should always have been subject to public scrutiny."

Manning famously leaked to Julian Assange a video showing a US Army Apache helicopter opening fire on a group of people in Iraq that included two Reuters journalists. 

The video was among thousands of documents, including diplomatic cables and warzone logs, that Manning passed to WikiLeaks founder Julian Assange, while working as an army intelligence analyst in Iraq in 2010.

"Instead of fighting tooth and nail to lock him up for decades, the US government should turn its attention to investigating and delivering justice for the serious human rights abuses committed by its officials in the name of countering terror," Brown said.

Manning faced up to 90 years in prison after he was convicted of 20 charges including espionage, theft and violating computer regulations by military judge Col Denise Lind in July.

Serve as a warning

Prosecutors asked for a minimum 60-year prison sentence to serve as a warning for other soldiers.

Critics argued that the sentence was too harsh when compared to those of US soldiers found guilty of torturing Iraqi detainees in the infamous Abu Ghraib prison and also other military personnel convicted of espionage.

"When a soldier who shared information with the press and public is punished far more harshly than others who tortured prisoners and killed civilians, something is seriously wrong with our justice system," said Ben Wizner, director of ACLU's speech, privacy and technology project.

"A legal system that doesn't distinguish between leaks to the press in the public interest and treason against the nation will not only produce unjust results but will deprive the public of critical information that is necessary for democratic accountability."

Manning will be eligible for parole after serving at least a third of his term.