MALABO, April 13 -- A desperate voice crackled down the phone-Mariano Nkogo Mba Nchama's 22-year-old son pleaded for help to get home to Equatorial Guinea from Ukraine, where he is fighting for the Russian army.

Daniel Angel Masie Nchama is among nearly 1,800 Africans fighting in the Kremlin's war on Ukraine; some signed up voluntarily in the hope of high pay, others say they were tricked or coerced.

"Come and help me! I'm on the front line in Ukraine, I'm fighting for Russia," he begged Equatorial Guinea's President Teodoro Obiang Nguema in an anguished voice message sent to his parents.

The recording has spread widely on social media and caused a strong reaction in oil-rich but poverty-stricken Equatorial Guinea, ruled with an iron f...