Teens as young as 13 held over Western Sydney baseball bat attack which left man in intensive care

Three teenage boys, including one as young as 13, have been arrested after a man was allegedly assaulted with what police believe was a baseball bat in Sydney's west overnight.

The 41-year-old suffered a serious head injury in the attack, which happened in Doonside, and is in intensive care in hospital.

He was allegedly hit in the head during a fight in Hammon Avenue about 7pm.

Three boys aged 13, 14 and 16, were later arrested and have been charged in relation to the assault.

All have been refused bail to appear in a children's court today.

The teens are believed to know the victim.