A priceless gold wreath has been unearthed in an ancient city in northern Greece, buried with human bones in a large copper vase that workers initially took for a land mine.

The University of Thessaloniki said in a statement Friday that the "astonishing" discovery was made during its excavations this week in the ruins of ancient Aigai. The city was the first capital of ancient Macedonia, where King Philip II _ father of Alexander the Great _ was assassinated.

Gold wreaths are rare and were buried with ancient nobles or royalty. But the find is also highly unusual as the artifacts appear to have been removed from a grave during ancient times and, for reasons that are unclear, reburied in the city's marketplace near the theater where Philip was stabbed to death.

"This happened quite soon after the original burial; it's not that a grave robber took it centuries later and hid it with the intention of coming back," excavator Chryssoula Saatsoglou-Paliadeli told The Associated Press. "It probably belonged to a high-ranking person."

The "impressively large" copper vessel contained a cylindrical golden jar with a lid, with the gold wreath of oak leaves and the bones inside.

"The young workman who saw it was astounded and shouted 'land mine!'" the university statement said.

Saatsoglou-Paliadeli, a professor of archaeology at the university, said the find probably dates to the 4th century B.C., during which Philip and Alexander reigned.

"Archaeologists must explain why such a group ... was found outside the extensive royal cemetery," the university statement said. "(They must also) work out why the bones of the unknown _ but by no means insignificant _ person were hidden in the city's most public and sacred area."

During the 4th century B.C., burials outside organized cemeteries were very uncommon.

In a royal cemetery at Vergina, just west of Aigai, Greek archaeologists discovered a wealth of gold and silver treasure in 1977. One of the opulent graves, which contained a large gold wreath of oak leaves, is generally accepted to have belonged to Philip II. The location of Alexander's tomb is one of the great mysteries of archaeology.

The sprawling remains of a large building with banquet halls and ornate mosaics at Aigai _ some 520 kilometers (320 miles) north of Athens _ has been identified as Philip's palace.

Aigai flourished in the 6th and 5th centuries B.C., attracting leading Greek artists such as the poet Euripides, who wrote his last tragedies there. The Macedonian capital was moved to Pella in the 4th century B.C., and Aigai was destroyed by the Romans in 168 B.C.