Experts have discovered a major network of underground funerary chambers and arches near the original site of an ancient obelisk in Ethiopia, UNESCO said.
The discovery was made last week during a surveying mission in the east African country in preparation for the return of the final piece of the 1,700-year-old Axum obelisk from Italy, the agency said.
Teams from the Paris-based United Nations Educational, Scientific and Cultural Organisation found the chambers using high-technology imaging equipment.
"It is likely that some of the tombs identified through underground imaging are intact," said Koichiro Matsuura, UNESCO's director-general, in a statement.
The Axum site was classified as a UNESCO World Heritage site in 1980. The obelisk - a symbol of African civilisation - was stolen in 1937 under orders from Italy's fascist dictator Benito Mussolini.
The vast chambers, part of a royal necropolis predating the Christian era, are located beneath a parking area built on the site in 1963, UNESCO said.
Italian researchers were examining images and were creating three-dimensional models of the royal tombs, the agency said.
An archaeologist has warned that re-erecting Ethiopia's ancient obelisk in the northern city of Axum could endanger the area's many royal tombs.
A new vast network of burial chambers has been discovered under a car park near the site where the Axum obelisk was to be restored in September.
(continued on BBC News)