Archaeologists in Israel said they had unearthed the oldest Hebrew text ever found, while excavating a fortress city overlooking a valley where the Bible says David slew Goliath.

Experts have not yet been able to decipher fully the five lines of text written in black ink on a shard of pottery dug up at a five-acre archaeological site called Elah Fortress, or Khirbet Qeiyafa.

The Bible says David, later to become the famed Jewish king, killed Goliath, a Philistine warrior, in a battle in the Valley of Elah, now the site of wineries and an Israeli satellite station.

Archaeologists at Hebrew University said carbon dating of artefacts found at the fortress site, about 20 km southwest of Jerusalem, indicate the Hebrew inscription was written some 3,000 years ago, predating the Dead Sea Scrolls by 1,000 years.

They have been able to make out some of its words, including "judge", "slave" and "king".

Yosef Garfinkel, the lead archaeologist at the site, said the findings could shed significant light on the period of King David's rule over the Israelites.

"The chronology and geography of Khirbet Qeiyafa create a unique meeting point between the mythology, history, historiography and archaeology of King David," Garfinkel said.