Nearly 20 pro-Pyongyang South Korean students broke into the US ambassador's residence in Seoul Friday, displaying banners demanding Harry Harris leave the country in an embarrassing security breach.

The students broke into the compound in the centre of the capital by climbing over the wall, pictures they posted on Facebook showed.

One image showed a group standing on the verandah of a hanok - a traditional Korean house - holding up banners reading "Harris leave this land", among others.

They said they were protesting against Washington's demands that Seoul increase its contribution to the cost of defending the South. The US stations 28,500 troops in the country to protect it against the nuclear-armed North, which invaded in 1950.

A police official told AFP: "17 students were taken to police stations for investigation after breaking into the ambassador's residence." The South's foreign ministry condemned the students in a statement, saying that "any harm or attack on foreign diplomatic missions cannot be justified under any circumstances".

Copyright Agence France-Presse, 2019