KABUL — Afghanistan today banned the use of a fertilizer chemical also used to make bombs, giving farmers and other holders a month to turn in their supplies.

President Hamid Karzai's office issued a decree banning the use, production, storage, purchase or sale of ammonium nitrate. The decision was made after an investigation showed militants had used the chemical in a series of bombings, according to a statement.

Violators who fail to turn in supplies will face court action, it said.

Fertilizer explosives were used in attacks that include the 2002 nightclub bombings in Bali, which killed 202 people, and the 1995 attack on a federal building in Oklahoma City with a 2-ton bomb that killed 168.

NATO-led forces already have been confiscating the chemical compound, urging Afghan farmers to use fertilizer containing urea nitrate instead. Ammonium nitrate fertilizer has been used to make about 95 percent of the bombs in Afghanistan, according to security think tank Globalsecurity.org.