Ukraine's army said five of its service personnel were killed this week, despite a ceasefire with pro-Russian separatists in the east of the country, taking the total number of deaths to 11 since the start of the year.
Three soldiers died when an unknown device exploded while they were moving to take up their position for duty on Sunday, the Ukrainian military said, the latest casualties of a six-year conflict that has claimed about 14,000 lives.
The deaths follow the killing of two Ukrainian servicemen by snipers as Ukraine's President Volodymyr Zelenskiy, who was accompanied by Western diplomats, was visiting the area.
Zelenskiy's office said in a statement the president had sent the country's defense minister and its chief of staff to eastern Ukraine to investigate the latest incidents.
During the second half of last year, there were four deaths after the sides agreed to a truce in order to give time for politicians and diplomats to seek a peaceful resolution.
Swedish Foreign Minister Ann Linde, who took over as rotating head of the Organization for Security and Cooperation in Europe, said during her first trip to the region in January that more steps are needed to protect the ceasefire.