Greece’s Prime Minister Antonis Samaras said archaeologists excavating an ancient mound in northern Greece have uncovered what appears to be the entrance to an important tomb from about the end of the reign of ancient warrior-king Alexander the Great.

Mr. Samaras, who visited the excavation on Tuesday, issued a statement saying the discovery “is clearly extremely important” and dates between 325-300 B.C.

Mr. Samaras said a broad road led to the tomb, while the entrance was flanked by two carved sphinxes. It was unclear how far archaeologists have reached.

Mr. Samaras said it remains to be seen who was buried in the tumulus, near ancient Amphipolis.