From Tuesday, "the formerly extensive access to NATO headquarters will be denied to all representatives of the Russian mission, except the Russian ambassador, his deputy head of mission, and two support staff," NATO said.

For any other delegation member, "standard visitor rules" will apply. "The staff member will have to be announced, registered and escorted during their visits," the alliance said.

Until recently, NATO cooperated with Russia on a range of projects, including anti-narcotics operations and helicopter maintenance in Afghanistan, joint plans to combat terrorism and anti-piracy initiatives.

NATO Secretary General Anders Fogh Rasmussen said last week that the projects in Afghanistan should be largely unaffected by the freeze in relations, but NATO officials have said off-the-record that they expect these to be curtailed.

Meetings between Russian officials and NATO have also been pared back to the ambassadorial level and above, allowing a political dialogue to continue but halting all discussions on practical matters.

The Russian mission, which numbers around 70 people, is "one of the biggest national delegations at NATO," an official for the alliance said on condition of anonymity.

The mission is based in a separate building on the compound to the one housing the 28 alliance members. Besides Russia, 21 other non-NATO countries are also represented on the site.

The Russian delegation has "always had more extensive access than NATO staff ever had in Moscow," the official said.

NJF/NJF