A Downing Street spokesperson said:
The Prime Minister called the South Korean President Moon Jae-In earlier this morning to congratulate him on his recent electoral success.
They agreed the UK and Republic of Korea would remain close partners on a wide range of issues, including trade, defence and security. They agreed the bilateral relationship would continue to go from strength to strength.
They agreed it would be important for the international community to continue to pursue a robust response to North Korean violations of UN Security Council resolutions and other international obligations.