Harper, in London for the Queen's Diamond Jubilee, says he is pleased Magnotta has been arrested.
"Well, I'm obviously pleased that the suspect has been arrested, and I just want to congratulate the police forces on their good work," Harper said.
Magnotta is facing five charges, including first-degree murder, in the slaying and dismemberment of Jun Lin, 33, a Chinese national who was studying at Montreal's Concordia University.
Lin's torso was found in a suitcase in a Montreal alley last Tuesday, and other body parts, including a hand and foot, were mailed to the offices of political parties in Ottawa.
The Berlin police force says Magnotta was nabbed without incident in the centre of the city.
Berlin police said officers caught up with Magnotta after someone recognized him outside an Internet cafe.
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