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Activists targeting Canada's Harper arrested in UK

Demonstrators pose with their banners for the media as they take part in an anti-tar sands protest outside the Houses of Parliament in London, timed to coincide with Canadian Prime Minister Stephen Harper addressing the British Parliament ahead of the G-8 summit, Thursday, June 13, 2013. Harper is the first sitting Canadian prime minister to formally address the British Parliament since the Second World War, when William Lyon Mackenzie King spoke in Westminster's Royal Gallery only weeks before D-Day. Harper thanked British Prime Minister David Cameron for his "robust advocacy" on behalf of a free-trade pact between Canada and the European Union during his address Thursday in London to British lawmakers. (AP Photo/Matt Dunham)

LONDON (AP) -- British police have arrested several environmental activists who allegedly breached Parliament security to protest Canadian Prime Minister Stephen Harper's visit.

The activists, who campaign against using oil from Canada's tar sands, say they entered the Parliament building and climbed onto its roof to protest as Harper visited to deliver a speech to lawmakers.

The Metropolitan Police said two men and a woman were arrested Thursday for trespassing on a protected site in Parliament. Two other women were arrested outside on suspicion of criminal damage.

Environmental groups have been pressuring Harper over tar sands oil, which they say is more of a threat than lighter forms of crude because of the dangers of spills and because it produces more of the greenhouses gases blamed for global warming.