Jordan's archaeology chief says he has a solid legal case to press for the return of 70 ancient lead books stolen and smuggled into Israel.

Ziad al-Saad says the relics could be the earliest Christian writing in existence.

If authenticated, he says they would be the most significant find in Christian archaeology since the discovery of the Dead Sea Scrolls in 1947.

He says there is strong evidence that the material was excavated in a northern cave by a Jordanian Bedouin five years ago. But they made their way into the hands of an Israeli Bedouin.

He said today that initial carbon and metallurgy tests performed by British experts date the material, depicting messianic symbols and written in archaic Hebrew, to the 1st century AD.