People watch a TV screen at a train station in Seoul, June 13, showing a news program reporting about North Korea firing an artillery shot into the Yellow Sea. Yonhap

North Korea fired an artillery shot into the Yellow Sea earlier this week, presumably from a multiple rocket launcher, a defense source here said Wednesday, as the U.S. has deployed six F-35A stealth fighters on the peninsula for combined drills.

The South Korean military had detected a single trajectory believed to be an artillery shot on Monday morning, the source said without providing additional details including where it was fired.

On Sunday, North Korea fired two suspected artillery shots from multiple rocket launchers. (Yonhap)