South Korea police investigate U.S. ambassador attacker's visits to North

U.S. Ambassador to South Korea Mark Lippert (3rd L) leaves after he was slashed in the face by an unidentified assailant at a public forum in central Seoul March 5, 2015. REUTERS/Yonhap

SEOUL (Reuters) - South Korean police said on Friday they were investigating possible links between a knife attack on the U.S. ambassador to Seoul and the assailant's multiple visits to North Korea, as they also sought to charge him with attempted murder.

U.S. ambassador Mark Lippert needed 80 stitches after his face was slashed at a forum discussing Korean unification in the capital, Seoul, on Thursday.