Ukraine's foreign ministry said on Thursday Niger's decision to cut diplomatic ties with Kyiv was "regrettable" and that Kyiv saw the move as based on groundless and untrue allegations.

Niger's junta said on Tuesday it was acting in solidarity with Mali which earlier broke off ties with Kyiv over remarks by a Ukrainian military intelligence official that it said showed Kyiv's support for rebels fighting in northern Mali.

"It is regrettable that the authorities of Niger have decided to terminate diplomatic relations with Ukraine without conducting any investigation into the incident in Mali or providing any evidence as to the reasons for such a step," the Ukrainian foreign ministry said.

Tuareg rebels said they killed at least 84 Russian Wagner mercenaries during fighting in July in what appeared the heaviest defeat for Wagner since it stepped in two years ago to help Mali's military authorities fight insurgent groups.

Wagner, a private army, played a major role in the war in Ukraine until last year when its forces mutinied in Russia and its leader died in an air crash a month later. It still has operations in a number of African countries.

The row stems from televised remarks by Andriy Yusov, a spokesperson for Ukraine's military spy agency, who said that Malian rebels had received the "necessary" information to conduct their attack.

In its statement, the Ukrainian foreign ministry said Kyiv rejected any allegations of its support for "international terrorism".

"The accusations against Ukraine cited in the statement by a representative of the government of (Niger) do not stand up to any criticism, are groundless and do not correspond to reality," it said.

Ukraine is locked in heavy fighting with Russia in the third year of Moscow's full-scale invasion, and trying to win over international support, in particular in the Global South.