Bangladesh police say they are making "substantial progress" in their probe into last week's nationwide spate of bombings as they question a detained Islamic leader. Intelligence officers were interrogating Maulana Fariduddin Masood, a senior member of the Jamiat Ulamaye Islam, a body of prominent Islamic clerics. He was arrested at Zia International Airport Monday. Police have also raided madrassas or Islamic seminaries since more than 400 simultaneous blasts rattled the country, killed two people and injured more than 100. Police are hunting for the leader of Jamayetul Mujahedin, Sheikh Abdur Rahman, saying many of the people interrogated have told them that he orchestrated the bombings. Reuters news agency reports from Dhaka that the banned group has posted a warning on a website, saying it will attack again unless the government introduces Islamic rule in Bangladesh.