JALALABAD, Afghanistan (Reuters) - Afghan police opened fire on protesters on Wednesday in violent demonstrations which left four dead and dozens wounded after a report that U.S. interrogators had desecrated the Koran, a health official said. U.S. troops stationed in the conservative Muslim city of Jalalabad, 130 km (80 miles) east of the capital, Kabul, were confined to base during the protest, witnesses said. Government offices in Jalalabad were set on fire, shops looted, and U.N. buildings and diplomatic missions attacked as thousands took to the streets, witnesses and officials said. Police fired to disperse crowds several times, witnesses said. Four people had been killed and 52 wounded, provincial health chief Fazel Mohammad Ibrahimi said after compiling information from three city hospitals. "Police had to open fire on the protesters, they were destroying the city," provincial police chief Hazrat Ali told Reuters. He declined to comment on casualties. About 1,000 school students demonstrated in nearby Laghman province. In Khost city, also in the east, protesters burned a picture of U.S. President George. W. Bush and a U.S. flag. There was also a report of a protest in Wardak province, southwest of the capital. Kabul was quiet. Newsweek magazine said in a recent edition that investigators probing abuses at the U.S. military prison in Guantanamo Bay had discovered that interrogators "had placed Korans on toilets, and in at least one case flushed a holy book down the toilet."