A man has shot and killed eight people, including two children, at a home in the US state of Pennsylvania before appearing to take his own life.

Police were called to a street in the city of Erie on Friday afternoon after witnesses reported seeing a man firing a gun before he entered a home, the Erie News Now outlet reported. Two women were reportedly found dead in the street.

The gunman then barricaded himself inside as police surrounded the building and ordered him to leave, but more gunshots were heard, the outlet reported.

When police entered, several more victims were found along with the gunman , who had an apparent self-inflicted gunshot wound.

The nine deaths were confirmed in a statement issued on Saturday by the mayor's office.

"Investigators have determined that all deaths occurred before officers arrived," it said.

"The deaths were not the result of any prolonged standoff or delay in police action."

Erie Police Chief Rick Lorah said that "there are no words that can adequately express the magnitude of the loss of life here.

He added that police "will not speculate about a motive or any information that could compromise this investigation".

Pennsylvania Governor Josh Shapiro said he had offered his administration's "full support following the tragic mass shooting in Erie last night - killing nine of our fellow Pennsylvanians".

"My heart breaks for this family," he said, adding that he and his wife "are praying for their loved ones and the entire Erie community".

The mayor is expected to hold a press conference on Saturday afternoon.