Two witnesses describe seeing the victims of a Melbourne stabbing crying for help.

Two people have been killed in separate stabbings in broad daylight in parks across two states.

A teenager has died and another is fighting for his life after both were stabbed in Melbourne’s northwest.

An 18-year-old man and 17-year-old boy were taken to hospital from Kings Park in a critical condition yesterday, but the 17-year-old died in hospital.

Police responded to reports that two males had been located with stab wounds on Main Road West in Kings Park just after 2.30pm.

Victoria Police say the exact circumstances surrounding the incident are unclear at this stage.

In a separate incident in Adelaide also on Saturday, a man was killed in broad daylight in a busy park in the city’s southern suburbs.

Police say the unidentified man, in his mid-to-late 30s, was found in the street with facial injuries from an altercation at a Hackham West park on Saturday afternoon.

Police and ambulance crews were called to the park off Corinth Rd just after 3.30pm, and the man was found in a bikeway and parkland area. Detective Superintendent Yvette Clark said locals and emergency workers performed CPR but the man died at the scene.

He had obvious head injuries, she said.

“There were a lot of people in the park today and it appears that the deceased man was seen in the park for an hour or two hours before he was later located deceased,” she told reporters.

Dept Supt Clark said witnesses saw up to two males with the man, and another witness saw a female with him.

“So it was a couple of local people who were in the area who saw him earlier on and then later when they came back located the male collapsed on the ground,” she said.

Dept Supt Clark said there were no suspects yet and appealed to anyone who was in the area between 11am and 4.30pm who may have information, footage or images to come forward.