REPRESENTATIONAL IMAGE: Protesters gather shouting slogans after burning a motorcycle during a general strike in Kathmandu January 20, 2015.Reuters

Nepal police opened fire on protesters as violence broke out ahead of the introduction of the new constitution, killing four people, including a four-year-old boy. 

Protesters resorted to throwing petrol-bombs at police vehicles on Tuesday in the Rupandehi district in Nepal's south, forcing police to open fire.

Four-year-old Chandan Kumar Patel was killed while he was playing outside his house in the area, The Himalayan Times reported.

"Four people were killed when police were forced to fire as the crowd became threatening," district police chief Rajendra Dhakal told AFP. 

Nepal's Constituent Assembly is likely to complete voting on the draft of the new national constitution by Thursday. The protest has seen violent flare-ups in recent months, claiming 40 lives across Nepal.

The new constitution is expected to divide Nepal into seven federal provinces, and protests have broken out over proper representation in the parliament.

Clashes had broken out on Monday after Nepal's lawmakers decided against making Nepal a Hindu nation again. Churches were torched and police stations attacked, ABC News reported.