US: F-16 fighter jets and black military helicopters in the sky, US Coastguard ships in the harbour, and police with assault weapons on the ground have turned Boston into a fortified city for the four-day National Democratic Convention, which gets under way today, writes Conor O'Clery in Boston.
Access to a "hard zone" around the FleetCenter where the convention is being held is restricted to visitors with accreditation, and garbage trucks have parked across access roads to keep unauthorised vehicles at a distance.
Authorities are taking unprecedented precautions against a possible terrorist attack on what is the first major political event in the United States since 9/11, amid fresh warnings that al-Qaeda may attempt to affect the political process.
Demonstrators have been consigned to a caged-in parking area beneath a low elevated track, which has led to furious protests.
The US Court of Appeals on Saturday refused to order the city to open up the "free-speech zone", despite the comment by District Justice Douglas Woodlock that to liken it to an "internment camp" was an understatement.
The largest protest organisations have called on their members to reject the site and rally in the surrounding neighbourhood instead.
The groups, which include United for Peace and Justice and the American Friends Service Committee plan to hold an anti-war rally on Thursday.
Some protesters appeared near the hard zone at the weekend with tape over their mouths to symbolise an infringement of their First Amendment rights to free speech.
Citing unconfirmed information, the FBI warned that a radical domestic group was planning to sabotage media vehicles with "explosive or incendiary devices."
Some local news crews have been kitted out as if for war, with Channel 7 issuing gas masks, bullet-proof vests and goggles to reporters and camera crews at "potentially volatile locations".
During a security sweep by the Secret Service of the convention centre, hundreds of journalists and news crews were kept waiting up to two hours to get inside.
One Democratic delegate from New Mexico has already suffered a violent blow since arriving in town. Mr David Smoak was hit on the forehead by a baseball during a game in which the Boston Red-Sox beat the New York Yankees on Saturday evening. He was not badly hurt.