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".
It had asked for security to be stepped up around the residence and the US embassy, it added.
The student group involved has previously said it would welcome North Korean leader Kim Jong Un if he visited Seoul.
The US embassy did not immediately respond to a request for comment.