US military prosecutors were to start presenting evidence on Monday against Army Private Bradley Manning in a court martial that has been widely criticised for its secretive nature.

Manning, a 25-year-old former intelligence analyst, has spent three years in detention awaiting trial since his arrest for leaking classified US documents to the WikiLeaks website.

Manning’s activist support network includes Daniel Ellsberg – the whisteblower in the 1971 Pentagon Papers case over US conduct in Vietnam. On Saturday, the network claimed to have drawn nearly 2,000 people to Fort Meade for a rally in Manning’s support.

Manning has pleaded guilty to several charges but still faces 21 counts, the most serious of which is aiding the enemy. He has admitted releasing hundreds of thousands of secret government files to WikiLeaks.

As the trial unfolds in the US, the recipient of Manning’s purloined classified material and founder of WikiLeaks, Julian Assange, is ensnared in his own legal problems in Britain.

Assange has been holed up in the Ecuadoran embassy in London since June 2012 after exhausting his appeals against extradition to Sweden, where he is wanted on sex abuse allegations. Ecuador has granted Assange asylum, but in order to travel there he would have to cross British territory and could be seized and extradited.

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