A minibus hit a landmine while crossing the border between Ukraine and the breakaway Donetsk region on Saturday.
The killing of two civilians and injuring a third, local authorities and witnesses said.
The bus, carrying three people, hit the mine after swerving off road in the buffer zone between two border posts, a statement on the breakaway Donetsk People’s Republic official website read.
The driver was killed along with one passenger.
The other passenger, a 61-year-old man, was being treated in hospital.
He told a Reuters journalist that the passenger who was killed was his mother.
The incident occurred near the village of Yelenovka, outside Donetsk.
The passengers were returning to the rebel-controlled region after collecting their pensions, the statement said.
Fighting broke out in 2014 between separatist forces in eastern Ukraine backed by Moscow and forces loyal to the pro-Western Ukrainian government in Kiev.
Despite an internationally brokered ceasefire that ended major fighting in 2015, deadly flare-ups of fighting occur regularly.
The unresolved conflict will be an issue when Ukraine holds a presidential election in late March.