Senior Muslim scholars, taking up Pope Benedict's call for a frank dialogue, have written him an open letter listing factual errors in his recent speech on Islam that sparked protest across the Muslim world.

The 38 experts, including grand muftis from the Muslim world and scholars based in Britain and the United States, said they accepted the Pope's stated regrets over the uproar and his expressions of respect for all Muslims.

The politely worded letter challenged the former theology professor on his own area of expertise and gave him poor marks for misreading the Koran, failing to use terms correctly and citing obscure and possibly biased sources.

Speaking in Regensburg in early September, Benedict quoted a 14th-century Byzantine emperor as saying Islam was evil and irrational and had been spread by the sword.

The speech sparked protests across the Muslim world, several churches were attacked in the Middle East and an Italian nun was murdered in Somalia. Benedict has said he did not agree with the emperor he quoted.

The scholars included grand muftis of Egypt, Oman, Uzbekistan, Istanbul, Russia, Bosnia, Croatia and Kosovo as well as a Shi'ite ayatollah, Jordanian Prince Ghazi bin Mohammad bin Talal and Western-based academics.