The UN has told Ukraine to withdraw its peacekeepers in Lebanon, saying some have engaged in "financial misconduct".
Ukraine had about 200 peacekeepers in Lebanon
It gave no details, but Reuters news agency quotes unnamed UN officials as saying the troops have been involved in reselling $1m (£0.54m) worth of UN oil.
The Ukrainian government says it has already taken disciplinary action against the soldiers responsible.
The Ukrainian contingent is part of the Interim Force in Lebanon (Unifil), which has 2,000 troops.
The Ukrainian unit consists mainly of engineers and landmine removers.
"The United Nations has initiated action to replace the Ukrainian unit in Unifil and is taking necessary measures to prevent recurrence," the UN said in a statement.
In Kiev the defence ministry said both the UN and Ukraine were "taking these events very seriously".
Ukraine says an investigation is underway. It also says it will continue to play a role in UN operations elsewhere in the world.