ATHENS -- Archaeologists in Greece have unearthed more than 1,400 ancient graves and tombs during excavation work for a new metro in the northern city of Salonika, the culture ministry said on Thursday.

The graves and tombs spanned an 800-year period from the fourth century BC to Roman times in the fourth century AD.

The finds range from humble pits and altar tombs of stone to marble sarcophagi, the ministry said.

One in five burial sites were found to contain offerings including Roman-era gold coins from Persia, jewelry made of gold, silver and copper, clay vessels and glass perfume-holders.

Founded in the fourth century BC by King Cassander of Macedon, Salonika was a major metropolis through Hellenistic and Roman times and possesses a rich archaeological heritage, some still undiscovered.

As in the case of the Athens Metro a decade ago, ongoing work on the Salonika underground has already brought other archaeological treasures to light.

In June, archaeologists found four gold wreaths and a pair of gold earrings in the grave of a woman who lived in the city over 2,000 years ago.

The metro also runs beneath the city's historic Jewish cemetery, which was one of the largest in Europe and is believed to hold more than 300,000 graves.

The 9.6-kilometer (six-mile) network is expected to be completed in 2012.