Berlin police say that Luka Rocco Magnotta is being questioned and will be brought behind closed doors before a judge, who will read out the international arrest warrant later.
Officers arrested him on the site, he did not put up any resistance. He says he is the wanted person.
Interpol has placed Magnotta, who was last believed to be in Paris, on the equivalent of its most-wanted list.
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The 53-year-old was killed shortly after leaving her home in Mosta, Prime Minister Joseph Muscat said.
Jordi Sanchez of the Catalan National Assembly and Jordi Cuixart of the Omnium Cultural group were jailed on Monday.
Storm Ophelia continues to bring strong winds to western parts.