Medieval stones have been stolen from the grounds of a hospital in Edinburgh.

The two 600-year-old relics, which are rare surviving examples of Scottish medieval art, were taken from Astley Ainslie hospital in the Grange.

The carvings originally adorned the Trinity Collegiate Church before it was demolished to make way for Waverley Station in the 1880s.

The church is significant as it was the site where the national covenant was first read to the people, an important moment in the political and religious life of Scotland.

Police are investigating the theft, which is thought to have taken place between late February and early March.

It is thought that whoever stole the 300kg artefacts may not realise their significance and could even be using them as garden ornaments.

Edinburgh City Council culture convener Richard Lewis said: "For an ancient capital city like Edinburgh, heritage crime is a real concern.

"These decorative stones may not appear like important architectural features to the untrained eye but they have been on the site of Astley Ainslie since the church was demolished in the mid 19th century.

"Any assistance the public can provide would be very welcome."

The council's archaeologist, John Lawson, said: "The stones are cylindrical and bear distinctive sculpted emblems of the Passion of Christ.

"They must weigh at least 300kg each and are about 45cm by 60cm wide.

"Whoever has removed the stones may be unaware of their historical significance. They could even be using them as garden ornaments.

"The stones are nationally important and are rare survivors of Scottish medieval art, therefore their loss is of great concern. We are appealing for their safe return."

Ron Finlay, an architect with NHS Lothian, said: "These historically important artefacts formed part of a collection of stones of ecclesiastical origin which are located within the Astley Ainslie Hospital site, and have been there for many years.

"They are a familiar sight to local people and we hope someone, somewhere can step forward with information. We are hoping for their safe return."

Police urged anyone with information to come forward.

Inspector Graeme Nisbet, of St Leonards police station, said: "We believe that the stones were taken from the grounds of the hospital sometime between February and March and are continuing to conduct enquiries into this.

"The stones are very distinctive and we would urge anyone who can help us establish their whereabouts to get in touch with us or report this information anonymously to Crimestoppers."