A 13-year-old boy has been left bloodied and bruised after being punched unconscious by a group of teens in Melbourne’s west.

The teen’s father, Troy, was preparing to go to work when he discovered the gang in the backyard of his Tarneit home about 11pm.

The gang suddenly became abusive, hitting the family with tree branches and rocks, before brutally targeting the 13-year-old.

A gang of youths attacked the 13-year-old boy. (9NEWS)

The boy is now recovering in hospital. (9NEWS)

“I feel angry, I just want to get them,” Troy said.

The victim’s mother, Mary, told 9News she found her son in “a pool of blood”.

“I rushed to him, held him.

“The world we live in is crazy but I didn't think it would be this crazy.”

The boy is now recovering from his injuries in hospital.

Hours later, police were called to an out-of-control house party at a rental property on Harmony Drive which was gate-crashed by youths.

Police have arrested four teens over the string of incidents in Tarneit overnight. (9NEWS)

Two 16-year-old boys from the western suburbs were arrested at the scene.

One was taken into custody for attempting to rob a teenage boy on his way home from work.

The other was arrested for criminal damage.

Just hours later, police returned to the street after reports a group of teenage girls were pelting a parked car with rocks.

“They were laughing saying "yeah, yeah that's what you get,” and then they ran,” resident Sandra Cortez said.

Two 16-year-old girls were arrested by police soon after.

Residents have said they are terrified after a spate of violent incidents in the area. (9NEWS)

Neighbours told 9News wild gatherings at the rental property are common and have left them terrified.

“(The offenders) were jumping on cars and everything,” resident Henrietta said.