Jakarta, Indonesia (CNN) -- They chanted "Osama, Hero! ... Obama, Terrorist! ... Destroy America!"

Hundreds of followers of the Islamic Defenders Front gathered Wednesday at its Jakarta headquarters to give Osama bin Laden "a million thanks and honor." They sang Islamic songs before chanting prayers for bin Laden.

Islamic Defenders Front, or FPI, is an Indonesian Islamist movement which advocates implementation of conservative laws. They're more known for thuggish attacks on groups deemed un-Islamic or immoral and minority religious groups, according to human rights groups.

Men, women and children filed into FPI's Jakarta headquarters, walking past posters of Osama bin Laden and U.S. President Barack Obama, his face crossed out in red.

In a statement read by its Secretary General Sobri Lobis, FPI expressed doubt about the death of bin Laden, saying the news from "infidel America" should be scrutinized. However, the group also said, if the news was true, it condemned the killing and the way bin Laden's body was buried at sea.

"Osama bin Laden is a true Islamic warrior figure who defended Islam," FPI said.