North Korea's Kim heads home after week-long visit to Russia

North Korean leader Kim Jong Un was heading home by train on Sunday, Russian news agencies reported, after a week-long visit to Russia that included talks with President Vladimir Putin on closer military and other cooperation.

A video published by Russia's state-run RIA news agency on Sunday showed Kim walking along a red carpet to his train carriage in the Russian Far Eastern city of Artyom, and waving goodbye to the sounds of a military band.

Artyom is about 254km from Khasan station on Russia's border with North Korea.

The trip by the North Korean leader, who seldom leaves his country, signifies "a fresh heyday of friendship and solidarity and cooperation is being opened up in the history of the development of the relations between the DPRK and Russia," North Korean state news agency KCNA said, using the initials for the Democratic People's Republic of Korea.

Russian Foreign Minister Sergei Lavrov said Moscow wanted to develop "equal and fair cooperation" with North Korea despite sanctions imposed on Pyongyang by the UN Security Council.

"We have not declared sanctions against North Korea, the Security Council did that. So appeal to the Security Council, and we will develop equal and fair cooperation with the DPRK," Lavrov said in a state TV interview, excerpts of which were broadcast on Sunday.

The Kremlin earlier said it abides by UN sanctions, but that it has a right to develop neighbourly relations, including in relation to sensitive topics.

The US and its allies worry about warming military ties between the two neighbours as Russia presses its invasion of Ukraine and North Korea, a reclusive communist state, proceeds with missile and nuclear development.

South Korea and the US say military cooperation between North Korea and Russia would violate UN sanctions against Pyongyang and that the allies would ensure there was a price to pay.

South Korean President Yoon Suk Yeol called such a military partnership "illegal and unjust", saying the international community would "unite more tightly" to cope with deepening ties between Moscow and Pyongyang, in written responses to the Associated Press on Sunday.

Yoon will head to New York on Monday for the UN General Assembly.

Well publicised visit

Russia has gone out of its way to publicise Kim's visit, dropping repeated hints about the prospect of military cooperation with North Korea, a country formed in 1948 with the backing of the Soviet Union.

On Saturday, Kim met Russian Defence Minister Sergei Shoigu, who showed the North Korean leader Russian nuclear-capable strategic bombers, hypersonic missiles and warships.

Kim and Shoigu "exchanged their constructive opinions on the practical issues arising in further strengthening the strategic and tactical coordination, cooperation and mutual exchange between the armed forces of the two countries and in the fields of their national defence and security," KCNA said on Sunday.

Moscow is discussing joint military exercises with North Korea, Shoigu told Russian media. He visited Pyongyang in July and toured a weapons exhibition with Kim, one of the most striking signs of deepening ties up to that point.

During his trip to Russia, Kim toured Russia's Pacific Sea Fleet, equipped with strategic nuclear submarines among other military vessels, KCNA said, quoting him as praising the fleet for its contribution to peace in the region. He was photographed visiting a control room and inspecting a warship.

This month, North Korea launched its first operational "tactical nuclear attack submarine".

Oleg Kozhemyako, governor of Russia's far eastern Primorsky region, gave Kim a bulletproof vest and six drones produced in the region, RIA news agency said.