Protesters infiltrated a nuclear-arms base in the Netherlands last week, days before leaders gathered to discuss atomic security less than 100 miles away.
Four members of the group "Disarm" entered the country's Volkel air base and photographed the exterior of a building possibly used to hold B-61 nuclear gravity bombs from the United States, the organization indicated in Dutch-language comments quoted by other activists. The installation is one of six bases in five European nations believed to hold such weapons, which Washington fields and maintains for the defense of its regional NATO allies.
The group stated that its members were arrested at 8:30 a.m. last Tuesday and interrogated.
Jeffrey Lewis, a nonproliferation expert at the Monterey Institute for International Studies, said the break-in and several prior incidents "would seem to demonstrate" vulnerabilities noted in a 2008 U.S. Air Force assessment of security at nuclear-arms facilities across Europe.
"This is very similar to a series of intrusions several years ago at Kleine Brogel Air Base by a Belgian peace group," Lewis wrote on Tuesday on the Arms Control Wonk blog.
He added, though, that it is unclear whether a B-61 storage vault is inside the structure photographed during last week's trespassing incident.
Publicly available maps of the facility "mark certain bunkers as having a [B-61] vault, although I don't know why they think they know that," the analyst wrote.
One Dutch-based activist said last week's infiltration was timed to coincide with preparations for the 2014 Nuclear Security Summit in The Hague, Netherlands.
"The activists want to raise awareness for the fact that the [summit] will talk about security of nuclear materials but not those nuclear materials that are used for military purposes," Wilbert van der Zeijden wrote in a blog post for the antinuclear group PAX.
NATO reportedly is poised to spend more than $154 million on security improvements at B-61 storage sites in the Netherlands, Belgium, Germany, Italy and Turkey. However, a number of critics have pressed for full withdrawal of the arms.