Kabul , Afghanistan ( CNN ) -- About 1,000 protesters gathered in front of Kabul University on Tuesday morning , as protests continue throughout Afghanistan to condemn the burning of a Quran by a pastor in the United States . The demonstrators marched toward the city center amid a heavy police presence but without incident , said Kabul City police official Abdullah Mahboob . The sight was in marked contrast to earlier demonstrations , some of which turned deadly . On Sunday , police and stone-throwing demonstrators clashed in Kandahar with as many as three people killed in the violence . At least nine people were killed and 73 injured in Kandahar on Saturday , and 12 people died Friday -- including seven U.N. employees -- when angry demonstrators stormed a U.N. compound in Mazar-i-Sharif . The demonstrations were sparked by the actions of a controversial Florida pastor who presided over what he called a trial of the Quran on March 20 . The holy book of Islam was `` found guilty '' by members of Jones ' tiny church and burned , according to a release posted on the church 's website . Afghan President Hamid Karzai strongly condemned the burning as did various U.S. officials , including U.S. President Barack Obama . `` The desecration of any holy text ... is an act of extreme intolerance and bigotry , '' he said Saturday in a statement released by the White House . `` However , to attack and kill innocent people in response is outrageous , and an affront to human decency and dignity . ''
The bomb went off without warning . Some other demonstrations have turned deadly . They have been sparked by a Florida mosque 's burning of the Muslim holy book .