The leader of Al-Qaida in Iraq has called on weapons experts to supply his fighters with biological weapons and dirty bombs.
In an audio recording posted Thursday on the Internet, a man who identified himself as Abu Hamza al-Muhajer also urged militants in Iraq to kidnap Western Christians to swap for a Muslim cleric jailed for life in the U.S.
Egyptian cleric Omar Abdel-Rahman was convicted of plotting to attack New York city landmarks, including the 1993 bombing of the World Trade Center.
The voice on the recording could not be independently verified.
In violence Thursday, more than 20 people were killed in Iraq. Bombings and shootings in and around Baghdad targeted civilians, Iraqi soldiers and police. Officials also reported finding 40 bodies showing signs of torture.
U.S. military intelligence officials warned that illegal militias are returning to Baghdad neighborhoods recently cleared by U.S. and Iraqi troops.
Some information for this report was provided by AFP, AP and Reuters.