U.S. Ambassador to South Korea Mark Lippert said Thursday that he is "in great spirits" after he was attacked by an individual on Wednesday.

"Doing well & in great spirits," he tweeted.

Lippert was attacked on Wednesday by a man reportedly wielding a knife. He cut Lippert in this face and hand, according to reports, and the media showed images of a bloodied Lippert being taken to his car.

The man is said to have yelled that he disagreed with joint military exercises between the U.S. and South Korea.

Lippert's injuries were not life-threatening, the State Department said. But Lippert received 80 stitches to his face, according to The New York Times. The newspaper reported that doctors said it would take several months for Lippert to fully recover.

The ambassador is a former adviser to President Obama who worked in his Senate office. An Iraq veteran, Lippert is also a former chief of staff for former Defense Secretary Chuck Hagel.

Sen. Rob Portman (R-Ohio) on Thursday tweeted his wishes for Lippert's speedy recovery.

Sen. Cory Gardner (R-Colo.), meantime, said he would be "carefully monitoring" the investigation.

—This report was updated at 10:55 a.m.