Moscow (AFP) — Russia’s ambassador to North Korea, who spent decades working in the reclusive state and recently oversaw a boom in ties between the two countries, died over the weekend, Moscow said Monday.

North Korea has become one of Russia’s closest allies during Moscow’s Ukraine offensive, with Pyongyang sending troops and weapons to help fight Kyiv.

Russia’s foreign ministry said Alexander Matsegora, who dedicated much of his life to boosting ties between the Kremlin and Pyongyang, died aged 70 on 6 December.

In a statement, it called Matsegora a “brilliant, talented man” who “devoted his entire life to selfless service to his homeland.”

Matsegora became ambassador to Pyongyang in 2014, having previously served as advisor at the embassy and as deputy head of the Russian foreign ministry’s Asia department.

Under his tenure, relations between the neighbors warmed to levels unseen since the Soviet era. Last year, President Vladimir Putin visited Pyongyang for the first time in more than two decades.

North Korean leader Kim Jong Un sent condolences to Putin over the ambassador’s “sudden demise,” state news agency KCNA reported Tuesday.

Kim said it was a “heartrending event and a great loss” — especially because it came as bilateral relations were entering a “crucial historic phase,” according to the news agency.

North Korea’s foreign minister Choe Son Hui also described Matsegora as a “precious comrade” and a “veteran diplomat of versatile talents and close friend of the DPRK people.”

During the Soviet period, Matsegora worked on trade ties between the USSR and North Korea.

Moscow did not say who will replace Matsegora.

Since last year’s Putin visit, Russian ministers have made regular trips to one of the world’s most secretive countries.