Australia's prime minister was hit on the head with an egg and a woman was knocked off her feet on Tuesday during a protest ahead of a general election next week, The Associated Press reported.

The egg appeared to strike Prime Minister Scott Morrison on the back of the head then bounce off without breaking as he spoke to voters at a hall in the regional town of Albury.

Bystander Margaret Baxter was knocked to the floor as security guards grabbed a 25-year-old woman who is accused of throwing the egg and carried her outside.

Morrison helped Baxter to her feet. He later suggested the protester was part of a militant movement that raids farms it accuses of cruelty to animals.

"My concern about today's incident in Albury was for the older woman who was knocked off her feet," Morrison tweeted.

"I helped her up and gave her a hug. Our farmers have to put up with these same idiots who are invading their farms and their homes," he added.

Baxter later said she had been knocked over by a cameraman. She said she landed on her hip but was not injured.

"The prime minister helped me get up off the floor and I was very grateful for his assistance," Baxter told Australian Broadcasting Corp.

"I recently had surgery on my stomach so my main concern was holding my stomach to make sure it didn't get hit or somebody land on it," she added.

Outside the hall, the protester told reporters she did not mean to knock anyone down.

The protester, who did not identify herself, described throwing the egg as "the most harmless thing you can do".

Police later said that the woman has been taken into custody and charged with assault.

The woman was charged with common assault and drug possession, after police found cannabis on her. She was released on bail and ordered to appear in court on May 27, Reuters reported.

No injuries were reported, the police said.

Opposition leader Bill Shorten condemned the protest as "appalling and disgraceful behavior".

"In Australia, we have violence-free elections," Shorten told reporters. "People are allowed to protest peacefully, but anything approaching violence is unacceptable."

Morrison was campaigning in an electorate held by his conservative Liberal Party. The federal election will be held on May 18.

In March, a teenager smashed an egg onto the head of a controversial right-wing Australian lawmaker who had blamed New Zealand's mosque shootings on its immigration program.

Agencies