A pro-government militiaman was killed while six others were wounded in separate explosions in the southern Philippines Monday, police said. Shortly before noon, suspects aboard a motorcycle tossed a fragmentation grenade into a busy street in downtown Cotabato city, local police chief Senior Superintendent Willie Dangane said. Six people, including a police officer, were hurt. One of them is said to be in a critical condition in hospital, Dangane said. Four hours earlier, a pro-government militiaman was killed when a powerful improvised explosive device was set off in front of a military detachment in the town of Upi, near Cotabato, the military said. No one has claimed responsibility for Monday's attacks, but military spokesman Lieutenant Colonel Jonathan Ponce said they suspected the separatist Moro Islamic Liberation Front (MILF) was behind the explosions. A so-called 'special operations group' of the MILF was blamed for a series of bombings that hit the volatile southern region early this month, killing at least eight and wounding over 100 others. The MILF broke a five-year-old ceasefire in August last year, carrying out simultaneous attacks across Mindanao after a proposed land deal with the government was rejected by the courts. Fighting that followed has since triggered a humanitarian crisis, with over half a million displaced and scores of civilians and fighters killed. 