RABAT, April 21 (Xinhua) -- The Islamic Educational, Scientific and Cultural Organization (ISESCO) on Sunday strongly condemned the deadly bomb attacks in Sri Lanka.

The ISESCO said in a statement that "this heinous act is a crime against humanity and an ugly face of hatred and extremism."

The attacks "hamper international efforts to promote the values of peace, coexistence and respect among followers of religions," it added.

Sri Lankan police said on Sunday that 13 people had been arrested over a series of blasts which killed 228 people across the nation.