Bradley Manning has been seen in public for the first time since he was arrested in Iraq in May 2010 for allegedly leaking hundreds of thousands of secret US state documents to WikiLeaks.

Security was exceptionally – some say bizarrely – tight at the opening on Friday of Manning's pre-trial hearing at Fort Meade in Maryland. Though a small number of seats in the military courtroom were reserved for members of the public, rigid reporting restrictions remained in place that prevent any live coverage of the proceedings.

The full charge sheet against Manning was released for the first time. It includes a total of 23 counts against the soldier, the most serious of which is that Manning knowingly gave "intelligence to the enemy, though indirect means".

The idea that WikiLeaks constituted an "enemy", or a conduit to an enemy of the US state, will in itself be subject of much debate and legal argument. A second charge follows a similar theme, and accuses of Manning of causing information to be published "having knowledge that intelligence published on the internet is accessible to the enemy".

Manning is charged with passing information from a secure database containing more than 250,000 records belonging to the US government – a reference to the US embassy cables that were published by WikiLeaks through a group of international newspapers including the Guardian in November 2010.

Another count refers to the first act of publication by WikiLeaks in February 2010 of a US embassy cable known as Reykjavik-13.

Aside from press and legal council, a small group of members of the public were allowed inside the courtroom. Admittance was decided on a first-come, first-serve basis. Those who got in had queued at the military base since "predawn", a military media liaison officer said.

A vigil in support of Manning was due to take place outside the main gates of Fort Meade to coincide with the start of the hearing. About 60 supporters were expected to attend. On Friday afternoon, the group is due to be joined by members of the Occupy Wall Street movement, who are travelling by bus to the military base. A further rally will be held on Saturday to mark Manning's 24th birthday. Daniel Ellsberg, who leaked the Pentagon Papers on the Vietnam war, will be addressing the protesters.

The army has come under criticism for taking so long to bring Manning to trial, and it faces further questions over how it is conducting the start of deliberations. The hearing is a preliminary stage, known as an Article 32, equivalent to a civilian pre-trial hearing, and is designed to assess whether the US soldier should be sent to a full court-martial.

Manning was charged in March with 37 counts relating to the leaking of hundreds of thousands of secret documents to WikiLeaks from secure US databases that he allegedly accessed while working as an intelligence officer at the Forward Operating Base Hammer outside Baghdad. The documents included Afghan and Iraq war logs, a trove of US embassy cables from around the world and video footage of a US helicopter fatally firing on a group of civilians in Iraq including two Reuters employees.

It was the largest leak of US state secrets in history and Manning faces a maximum sentence of life in custody with no chance of parole. Technically, Manning could also face the death penalty on the count of "aiding the enemy", but prosecutors have made clear they will not seek the ultimate punishment.

Among the stranger aspects of the pre-trial are that it begins on a Friday and will run throughout the weekend. The military authorities have indicated that each day's proceedings could be extended late into the night.

"To run the hearing through a weekend right before the Christmas vacation is clearly designed to minimise both media coverage and public protests," said Jeff Patterson of the Bradley Manning support network.

Patterson added that in his view the tight security around the case was an attempt to cast Manning as a dangerous individual. "The prosecution are pushing for a sentence of life with no parole, so they have to portray him as someone who deserves such extreme punishment."

Reporters will be allowed virtually no access to the world outside the base while the court is sitting. There are also likely to be periods when the Article 32 goes into private session to deliberate on matters that the army regards sensitive to national security.

Under the military system, the proceedings will be led by an army official known as an investigating officer, whose duty will be to recommend at the end of the hearing whether Manning should move on to a general court-martial or face a lesser punishment.

Manning's defence lawyer, David Coombs, has made official protestations that most of the witnesses he wanted to call have been declined by the military. Coombs had issued a list of 48 witnesses that he had wanted to summons, including Barack Obama, Hillary Clinton, Manning's superiors and psychiatrists who assessed the soldier's mental and emotional state of health before the WikiLeaks transfer of secrets occurred. But only 10 of the listed individuals were accepted, all of whom were also on the prosecution's wish-list of witnesses.

In a filing, Coombs complained that any attempt by the military to block defence witnesses "would deny PFC Manning his right to a thorough and impartial investigation and turn this into a hollow exercise". The lawyer added that Manning's charges were "among the most serious charges that a soldier can face. The government must be prepared to accept the costs incurred by the seriousness of the charges that they have preferred against PFC Manning."