The embassy "advises Chinese nationals in South Korea to remain calm, monitor developments in South Korea's political situation, enhance safety awareness, limit unnecessary outings, exercise caution when expressing political opinions," it said in a statement.

South Korea's President Yoon Suk Yeol on Tuesday declared emergency martial law, saying the step was necessary to protect the country from "communist forces" amid parliamentary wrangling over a budget bill.

"To safeguard a liberal South Korea from the threats posed by North Korea's communist forces and to eliminate anti-state elements... I hereby declare emergency martial law," Yoon said in a live televised address to the nation.

Yoon in November met with his Chinese counterpart Xi Jinping in person for the first time in two years on the sidelines of the Asia-Pacific Economic Cooperation summit in Peru, where he called for greater cooperation with Beijing on "regional peace and stability", the Yonhap news agency reported.

China is a key ally of North Korea, with whom Seoul remains technically at war and whose leader Kim Jong Un has engaged in escalatory rhetoric and military posturing this year.