The EU's diplomatic chief Federica Mogherini on Monday called for "no external interference" in Lebanon, after the country's prime minister resigned unexpectedly, triggering rumours he was being held against his will in Saudi Arabia.

"We expect no external interference in this national agenda and we believe it is essential to avoid importing into Lebanon regional conflicts, regional dynamics, regional tensions that have to stay out of the country," Mogherini said, adding that she would meet Lebanese Foreign Minister Gebran Bassil in Brussels on Tuesday.