North Korea has unveiled for the first time what it says is a nuclear-powered submarine under construction, a weapons system that can pose a major security threat to South Korea and the US.

The announcement came amid fears that Pyongyang may be receiving crucial military technology from Russia in return for sending troops and weapons for its war against Ukraine.

North Korea revealed Saturday it is building a nuclear-powered submarine — a weapon that experts say would be “absolutely threatening to [South Korea] and the US.” Images showed Kim Jong Un touring a navy shipyard to see the massive warship,

South Korean President Yoon Suk Yeol, who lawmakers voted to impeach, was released from detention Saturday after spending nearly two months in custody under a criminal probe for his martial law declaration.

South Korean President Yoon Suk Yeol left a detention centre in Seoul on Saturday, after prosecutors decided not to appeal a court decision to cancel the arrest warrant of the impeached leader.

South Korea's impeached president has been released from detention after a court in Seoul overturned his arrest on technical grounds. Yoon Suk Yeol walked free on Saturday to cheers from his supporters - but still faces trial on insurrection charges after his failed attempt to impose martial law in December.