YEREVAN, Armenia — Three workers of the HALO Trust de-mining organization have been killed and two injured in a mine explosion in Azerbaijan’s separatist Nagorno-Karabakh region.

All the victims were local residents, the presidential administration of the unrecognized republic said.

Nagorno-Karabakh has been under the control of ethnic Armenian forces since a 1994 cease-fire. Azerbaijan claims that Armenia’s military also has troops in the region.

HALO said the Thursday morning blast occurred when the workers were surveying an area to remove explosives and their vehicle ran over a mine.