Three emergency workers from Zhytomyr Oblast were killed demining in Kherson Oblast on Dec. 24, the State Emergency Service of Ukraine said in a Facebook post.
The workers had gone to Kherson Oblast to assist with the demining process after parts of the oblast were liberated by Ukrainian forces.
They were killed by Russian mines that exploded during the demining process, according to the post.
Serhii Kruk, who heads Ukraine's State Emergency Service, said about 30% of Ukrainian territory is mined.
On Nov. 14, Kherson Oblast Governor Yaroslav Yanushevych said that Russian troops had mined "nearly everything" in the recently liberated Kherson and asked people to avoid gathering in the central part of the city as sappers needed to demine it first.
Ukrainian forces liberated parts of Ukraine's southern Kherson Oblast, including the regional capital Kherson, on Nov. 11.