Justin McCurry reports for the Guardian from Tokyo

The inclusion of a mutual defence clause in their comprehensive strategic partnership, finalised on Wednesday after hours of talks in the North Korean capital Pyongyang, will add to alarm in the West over growing economic and military ties between North Korea and Russia.

It wasn’t immediately clear what form that support might take, and no details of the agreement were initially made public. Vladimir Putin later described the pact as “defensive”, citing North Korea’s right to defend itself, according to Tass. He added that Russia would not rule out developing military-technical cooperation with North Korea.

Speaking after a signing ceremony, Kim Jong-un called the deal the “strongest ever treaty” signed between the two countries, elevating their relationship to the level of an alliance. The pact would lead to closer political, economic and military cooperation, he was quoted as saying.

He hailed the agreement as a “significant and historic moment”, adding, “I have no doubt it will become a driving force accelerating the creation of a new multipolar world.”

In Washington, the US secretary of state, Antony Blinken, had earlier said Putin’s visit highlighted Russia’s attempts, “in desperation, to develop and to strengthen relations with countries that can provide it with what it needs to continue the war of aggression that it started against Ukraine”.