"Canada grieves with our Swedish friends in this hard time and we offer all possible assistance", the prime minister said in his statement on Friday.
The Stockholm suspect, aged 39 and from the Central Asian republic of Uzbekistan, applied for permanent residence in Sweden in 2014.
Police have arrested a 39-year-old Uzbek man who was known to the Swedish security services, but had no known links to extremist groups.
Dan Eliason, head of Sweden's National Police, told a news conference Saturday that "there is nothing that tells us that we have the wrong person".
A woman handed out roses to two police officers guarding the square: "thank you", she said and smiled.
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ADEC says the time of the spill is unknown but it was reported Friday morning. "However it is not now spraying crude oil". The site was also venting natural gas from two locations: a leak near the top of the well, and another lower down.
At least four people were killed and 15 injured Friday after a stolen beer truck drove into a crowd of people outside a department store in the center of Stockholm, in what the Swedish prime minister has suggested was a terrorist attack, according to media reports.
The vehicle mowed down shoppers before slamming into the facade of the busy Ahlens department store.
The official police Twitter account said one man had been arrested and police Chief Vidar Pedersen said police were working to disarm the device, which was found on the street outside the Groenland station.
Police also said about five people of interest remain in police custody.
"I am urging the public to be vigilant and keep updating the police", Lofven said. Sweden's crown princess Victoria held back tears as she left flowers for the victims at the site of the attack on Saturday.
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The shop - which caught fire whena beer lorry smashed into its entrance during Friday's terrorist attack - sent an email to all customers saying it would "begin a sale of smoke-damaged products".
"We follow developments but as of now our thoughts go to the victims and their families, " he said. It said two were in intensive care, four were seriously injured but the one child was not seriously hurt.
The driver fled from the truck, prompting lockdowns at Parliament and the city's subway system as police looked for the suspect.
Several police cars parked near the scene were also covered in flowers by Swedes, who widely praised the emergency crews' speedy response to the attack.
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Turkey's foreign minister said Sunday that Turkey has no obligation to take a side in any dispute between the USA and Russian Federation .