Spokesman to Ukraine's foreign ministry, Oleg Nikolenko, urged African countries to press Russia not to use their citizens in Moscow's war in Ukraine.

"We call on African Union and all African states to demand that Russia stop press ganging their nationals," Nikolenko wrote on social media.

"Africans shouldn't die for Putin's sick imperial ambitions," he said.

Zambia's foreign minister on Monday said a Zambian student who had been jailed in Russia died in fighting in Ukraine, and demanded an explanation from the Kremlin.

Lemekhani Nathan Nyirenda, 23, who had been serving a prison sentence in Moscow, "passed away on 22nd September 2022, in Ukraine," minister Stanley Kakubo said in a statement, adding he died "at the battlefront."

Ukrainian officials say the Wagner mercenary group has been sending thousands of soldiers recruited in Russian prisons to the front line, with the promise of a salary and an amnesty.

Several Ukrainian soldiers on the front line in Bakhmut in eastern Ukraine told AFP last month that alleged ex-convicts were being used as bait to draw fire and reveal Ukrainian positions.