Hundreds of skeletons could be buried beneath Oxford's Bonn Square, according to the archaeologist overseeing redevelopment work.

Earlier this month the city council launched a £1.5m redevelopment of the square in a bid to tidy up a run-down part of the city centre.

This week, as construction firm English Landscapes started digging up the site with bulldozers, skeletal remains, which could date back to the 12th century, were found on the former burial site.

Andy Norton, of Oxford Archaeology, who is in charge of ensuring human remains are properly reburied once they are uncovered, said: "There could be hundreds of skeletons on the site because the church of St Peter-le-Bailey dates back to the 12th century.

"The original church was knocked down in the mid-18th century and a new one was constructed in the mid-19th century.

"We will remove and rebury any remains we find. There has been so much disturbance we may have to remove bones for storage and rebury them later.

"The work clearly needs to be handled in a sensitive way. We have already had an angry call from a resident to say that we are digging up about 90 of his ancestors.

"We will stay in touch with him and if we find any gravestones with his ancestors' names on we will invite him to witness the reburial."

Mr Norton said a number of brick graves had been discovered on the site, which date back to the 18th and 19th centuries.

He added: "Most people buried on the site were ordinary Oxford residents, they were not rich or famous. But the presence of these graves indicates a display of wealth.

"These brick graves were constructed as a display of wealth and because they were less likely to be disturbed by grave robbers."

The council said archaeological work prompted by the discovery was not expected to hold up the redevelopment, due to be completed this summer.

Council spokesman Chris Lee said the Oxford Diocese gave permission in 2004 for the redevelopment of the square on condition that bones were reburied after examination.

In 2003, the county council had to spend an extra £300,000 to pay for an archaeological dig when hundreds of skeletons were found during the redevelopment the Oxford Castle.

Earlier this month, the siege of Bonn Square came to an end when tree-top protester Gabriel Chamberlain came down from the branches after 11 days.

Protesters wanted to stop the felling of trees before redevelopment work began.

Yesterday, it emerged that the security operation, including security staff, fencing and lighting, had cost the council £11,700 - about £1,000 a day.

City council spokesman Louisa Dean added: "We are working with Oxford Archaeology to make sure that great care is being taken at Bonn Square."