South Korea's spy agency says North Korea appears to have sent more troops to Russia, after its soldiers deployed on the Russian-Ukraine fronts suffered heavy casualties.

Ukrainian troops holding positions in Kursk say the North Koreans have reappeared on the battlefield and become even more formidable foes.

Finance ministers and central bankers from the G20 top economies gather in South Africa on Wednesday and Thursday, for a meeting marred by the absence or curtailed attendance of key members and disputes over the main issues of climate, debt and inequality.

In addition to the contingent that is fighting alongside the Russian forces, Pyongyang has sent millions of artillery munitions and other security assistance to Moscow.

Two North Korean soldiers captured in January in the Kursk region are currently receiving medical treatment. They are testifying about North Korea's involvement in the war on Russia's side, The Wall Street Journal reports.