Intruders wearing balaclavas broke into the Russian offices of Greenpeace overnight, the environmental group said Friday as 30 of its activists continued to be held in a nearby prison on charges of piracy.
Security images released by the organization appeared to show a number of men scaling a fence and breaking into the offices in Murmansk, a port city northwest of Moscow.
Russian authorities arrested the international crew of a Dutch-registered Greenpeace ship on Sept. 19 after it protested a Russian oil platform in the Arctic. They are charged them with piracy, which carries a sentence of up to 15 years in jail.
The American captain, Peter Willcox, 60, and his crew of 30 protesters were detained a day after some of them tried to climb the Prirazlomnaya oil rig, which Gazprom, the state oil company, operates in the Arctic Ocean near the tiny settlement of Verandey.
They remain in a Murmansk jail.
Kathy Cumming, a London-based spokeswoman for Greenpeace, said the only item stolen was a replica cage that was due to be used at a demonstration highlighting the plight of the detainees.
Earlier this month, the Netherlands launched legal proceedings against Russia, saying it had unlawfully detained the ship's crew.
It marked an escalation in tension between Russia and the Netherlands.
On Wednesday, Dutch Prime Minister Mark Rutte's government summoned Russia's ambassador in The Hague to explain an assault on a Dutch diplomat in Moscow.
The second-in-charge of the Dutch embassy was attacked at his home by unknown intruders posing as electricians.
Last week, Dutch Foreign Minister Frans Timmermans had to apologize after a Russian diplomat was detained in the Hague. Russia had complained that he was assaulted during the detention.
Rutte told journalists the incident in Moscow was "very serious," and the attack was condemned by the United States.
"We condemn the attack on the minister-counselor of the Netherlands in Moscow. Such actions are unacceptable.," U.S. Ambassador to Moscow Michael McFaul said on Twitter.
The Associated Press contributed to this report.