Police said Friday they arrested a man for allegedly posting a letter on the White House homepage threatening to kill the top U.S. envoy in Seoul.

The 33-year-old, identified only by his surname Lee, is suspected of writing the letter threatening to kill U.S. Ambassador to South Korea Mark Lippert earlier this month, the Seoul Metropolitan Police Agency (SMPA) said in a press release.

After receiving a request for an investigation from the White House, police arrested the man at his home in Seoul on July 14.

On Lee's confiscated laptop, records of access to the homepage were found, as well as a draft of the letter and a screen capture taken as he allegedly wrote the letter on the website, the release said.

Lee denies the charge that he wrote the letter and seems to have no accomplices, the release said.

After creating their profile, police concluded that Lee lived in seclusion and spent most of his time surfing the Internet, as he failed to find a job after graduating from university.

Lippert was attacked with a knife at a breakfast function in Seoul on March 5, which left him with deep gashes on his face and arm that needed more than 80 stitches.

Kim Ki-jong, who attacked the envoy, is standing trial over allegations of violence against a foreign envoy, attempted murder, business obstruction and sympathizing with North Korea in violation of the National Security Law. (Yonhap)