A 400-year-old iconic mosque in Iran's central city of Isfahan listed as a UN World Heritage Site has been damaged during restoration work, officials said Monday.
The 17th century Shah Mosque, also known as the Royal Mosque, was built during the "golden age" of Isfahan, the capital during Safavid dynasty.
"Supervisors and restorers realised there was damage, especially in the upper part of the dome," said Alireza Izadi, head of the heritage for the city, according to state media.
The mosque forms one of four dramatic buildings in the vast Naghsh-e Jahan Square in the heart of the city, also known as Meidan Imam. The square complex was listed by the UN cultural organisation UNESCO as a World Heritage Site in 1979.
UNESCO says the mosque is of "particular interest", and "remains the most celebrated example of the colourful architecture which reached its high point in Iran under the Safavid dynasty".
Experts quoted in Iranian media said the designs of flowers on the restored tiles do not match each other, and the patterns on the dome are not aligned.
"We are going to replace the dome tiles, because the weight of the scaffolding has damaged their edge," Izadi told the official IRNA news agency.
The restorer of the project, Mehdi Pakdel, told state television he had acknowledged "mistakes" had been made, while noting that his "work was not yet finished".
Pakdel said problems with the scaffolding used during restoration work, as well as the challenges of working high on the dome up to a height of 54 metres (177 feet) were "among the causes" of the mistakes.
"The contractor of the project, who is one of the veterans of restoration in Isfahan, has said he is ready to take the necessary measures to repair the defects as soon as possible," Izadi added.
Isfahan, the third biggest city in Iran, is one of the key tourist destinations in the country.