A drone crossed from Romania into Bulgaria and exploded near the Trans-Balkan gas pipeline. The blast has sharpened NATO border security concerns even as officials see no sign of intent.

The incident would be raised at a meeting of the North Atlantic Council early next week, Bulgaria's Defense Minister Dimitar Stoyanov said.

The incident would be raised at a meeting of the North Atlantic Council early next week, Bulgaria's Defense Minister Dimitar Stoyanov said.

A drone entered Bulgarian airspace on Saturday and exploded close to an international gas pipeline shortly after crossing the border from Romania. There were no casualties or damage.