Swedish police detained three suspects in Stockholm. All three men are Swedish citizens. Norwegian authorities arrested three men in Oslo but did not release any information about them.
Norwegian news media reports say the suspects are of Somali origin.
Norway's police intelligence agency (PST) said the agency would seek permission to hold at least one of the suspects in custody.
Last month, the agency said violence by Islamic extremists would pose a significant challenge to Norway's security in the coming years, partly due to the country's participation in NATO-led peacekeeping operations in Afghanistan.
Norway has about 500 soldiers in Afghanistan.
Source: By VOA News
