Sergeant Tony Woodbridge said about a dozen protesters gathered outside Waitaki MP Miles Anderson’s office in Thames St yesterday morning.
Police were called to the scene about 10.15am after "a small number" of the protesters forced their way into the office, Sgt Woodbridge said.
One of the protesters allegedly grabbed an office worker by the arm and pushed her out of the way, he said.
The 39-year-old Dunedin woman was subsequently arrested and charged with assault.
She would appear in the Oamaru District Court next month, Sgt Woodbridge said.
While the victim was "shaken and a wee bit upset" she suffered no injuries.
The protesters were removed from the office after initially refusing, he said.
Protesting should be done peacefully and legally, Sgt Woodbridge said.
"The police understand and support people protesting when it’s done in a legal manner and when no-one is placed in harm by that protest.
"There’s no excuse for that kind of behaviour from anyone."
Mr Anderson said the incident was "a bit surprising for Oamaru".
"There’s been a number of protests outside my office over the last two years and all the others have been respectful.
"People that think that sort of behaviour is acceptable need to take a good look in the mirror.
"I just think it’s not OK to intimidate someone like that."
He said the victim was the only member of staff in the office at the time.
The protest in Oamaru was one of nine happening across the country, organiser Aotearoa for Sanctions said in a statement.
In its press release, the group described itself as a "collective of constituents" demanding sanctions on Israel.
"This comes after most of our requests for meetings about Israel’s genocidal crimes were ignored or denied," it said.
The group was urging MPs to support the Unlawful Occupation of Palestine Sanctions Bill and advocate cutting all ties with Israel.
"This government calls itself ‘tough on crime’ yet continues to ignore the most horrific crime of all — genocide," the group said.
