Portland police Acting Detective Sergeant Jason von Tunk, of the crime investigation unit, said a number of men armed with baseball bats and other implements entered a Waratah Crescent home about 5.15pm.

The man aged in his 30s was severely beaten, suffering injuries to his face, arms, legs and body.

A 17-year-old female was also attacked and suffered serious back injuries.

Both were transported to the Portland hospital for treatment.

The man was stablised before being flown by helicopter to Melbourne's Alfred Hospital about 9pm last, where he is reported to be in a serious but stable condition this morning.

The teenage girl remains in the Portland hospital.

Acting Detective Sergeant von Tunk said the incident was possibly drug-related and he called for information from the public.

"This severe beating, which resulted in serious injuries all happened in the presence of of a nine-year-old boy. It must have been a horrifying experience for him and the two victims," he said.

"It's usual for an aggravated burglary to be committed with such intensity. It's very worrying and when these sort of things happen and innocent people can be involved."

Acting Detective Sergeant von Tunk said that police had been unable to speak to either of the victims due to the severe nature of their injuries.

"Police are requesting anyone with any information to contact Crime Stoppers 1800 333 000 or Portland police station," he said.