A man wielding a knife tried to attack Finnish Prime Minister Jyrki Katainen in the south-western town of Turku on Monday, but was swiftly arrested by police, the prime minister's office said in a statement.

"Prime Minister Katainen's security men have apprehended a person who had brought a sharp weapon to Prime Minister Katainen's electoral meeting in Turku," said the statement.

"The Prime Minister was not injured and the programme will continue as planned."

Security guards quickly swooped in to protect Katainen, 41, and removed him from the scene. He returned shortly afterwards to resume campaigning.

A young "disheveled"-looking man had approached the prime minister to shake his hand, saying he was in a difficult situation and needed help, newspaper Hufvudstadsbladet reported.

"Then the man went down on his knees, pulled out a knife and said something about killing," photographer Robert Seger, who witnessed the event, told the daily.

Katainen had been discussing taxes on diesel and the taxes paid by the elderly before the incident.