Update 15:20
Swedish Prime Minister confirms that one person has been arrested.
Update 15:07
Police in Sweden now say that at least two people have died and several more injured, after a truck was driven into crowds in Stockholm.
There's also reports of shots being fired.
Swedish authorities are treating it as a deliberate attack.
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Update 14:27
Local media are reporting that three people have died.
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There's reports a truck has been driven into people in Stockholm.
An area in the city centre has been cordoned off as a result.
More to follow.
