The BBC's Cary Johnston: "The staff have been shocked by the raid"

Durham Police fear thieves targeted Durham University's library and forced open glass-topped display cases to steal two manuscripts and five books, some of which are hundreds of years old.

The rare collection of Shakespeare works was a first folio edition published in 1623. Also included in the haul was a 15th century manuscript, including a fragment of a poem written by Geoffrey Chaucer, the author of The Canterbury Tales.

A police spokesman said: "Experts say it is impossible to put an exact price on them but estimate their value at about £250,000."

Shakespeare's rare folio was published in 1623

However, a report in Saturday's Daily Telegraph puts the value of the Shakespeare folio at £1m alone.

Staff at the library, situated just yards from Durham Cathedral, discovered the theft when they opened on Thursday.

University spokesman Keith Seacroft said it was not clear how the thief had managed to get the manuscripts and books out of the library without being noticed.

He said: "We are shocked and distressed by the theft. The manuscripts and books are a unique and irreplaceable part of the region's heritage.

"It would be virtually impossible to sell them to legitimate buyers."

Exhibition

Detective Inspector Andy Summerbell, of Durham City Police, said: "It is likely that whoever was responsible will have identified a buyer for such a highly-specialised haul.

He said the library did not appear to have been broken into and police are looking at the possibility that the theft was carried out when the library was open.

The thieves also got away with two works by the 10th century poet Aelfric, printed in 1566, an edition of Beowulf printed in 1812 and a 1612 book of maps and poetry.