South Korean President Yoon Suk-yeol said on Friday it was necessary to ensure Russia’s invasion of Ukraine does not succeed and that Seoul was considering its options when it came to lethal aid to Kyiv.

In a speech at Harvard University's Kennedy School on the fifth day of a state visit to mark the 70th anniversary of the U.S.-South Korean alliance, Yoon said the Russian invasion was a violation of international law and the rights of Ukrainians.

"We should prove that such attempts will never reach success, to block further attempts being made in the future," he said, according to simultaneous translations of his remarks.