Russian-backed rebels in eastern Ukraine have released two American aid workers they detained along with more than 30 others during an armed raid on the Donetsk offices of the International Rescue Committee (IRC), officials with the self-proclaimed Donetsk People’s Republic said on Saturday. A rebel leader accused the two of spying for the United States, and the group was taken into custody on April 29. The pair of Americans are reportedly now in a safe location.

“We have freed two Americans that we arrested earlier. One of the two is a CIA agent, the other was enlisted,” said Alex Zakharchenko, known as the prime minister of the DPR.

Shortly after the April raid, Zakharchenko said that his security outfit found clandestine listening devices hidden in the IRC’s Donetsk office. He did not offer proof to back the claim, but said that the devices “were seized and handed over to the American authorities,” without further specification. Zakharchenko also accused the IRC of not paying taxes to Donetsk.

The raid on the IRC attracted widespread condemnation from rights organizations and prompted the aid group with headquarters in New York and London to suspend its program in Ukraine’s war-torn east, where locals have been devastated by a bloody conflict between the rebels and Ukrainian government forces. Masked men armed with assault rifles detained 37 IRC staff during the operation, all but seven of whom were local Ukrainians. Five of the foreign staff were immediately thrown out of the DPR, but rebels held onto the two Americans.

The IRC is a catch-all aid group that provides health care and economic and educational aid, among other servics, in 40 countries and is considered a top group worldwide in terms of efficiency and effectiveness in operations.

“The actions taken by the security forces of the self-proclaimed Donetsk People’s Republic, including the intimidation of our dedicated humanitarian staff, are an affront [to the IRC’s] principles,” said IRC head and former British Foreign Secretary David Miliband on Saturday. “Every day, the world’s humanitarian workers show great courage, taking risks to help the most vulnerable in crisis situations. They should never be targeted.”

Fighting in eastern Ukraine has calmed somewhat following a February ceasefire signed between warring sides, but months of fierce fighting has left the eastern region of Donbas in ruins. More than 6,00 people have been killed and 1.2 million displaced because of the fighting, according to the United Nations. Most of the locals who didn’t flee the fighting were left to brave seemingly endless artillery barrages without electricity, heat or medical supplies. Many aid groups working in the region have reported similar tactics of intimidation by both rebels and government-backed militias.

The east remains tense, with both Ukrainian government forces and rebel forces massing large batteries of heavy artillery, troops and equipment behind a ceasefire line agreed upon in February, poised to resume fighting. Rebels held a large military parade on Saturday to celebrate Victory Day, one of Russia’s biggest holidays commemorating the Allied victory over Germany in the Second World War.