The supermarkets targeted were all Swedish, but sell American goods
Three supermarkets have been destroyed and a fourth damaged in central Sweden in what police say might have been a series of anti-American arson attacks.
Police spokeswoman Kia Samrell said more than 100 firefighters were called in to put out the fires overnight at the Swedish supermarkets in Sodertalje.
Ms Samrell said the police were investigating whether the left-wing group, Global Intifada, was connected.
Global Intifada claimed responsibility for two fires in Sodertalje last year.
It has also said it was behind arson attacks on vehicles belonging to the Danish and Russian embassies in 2005, and an attack on a Polish consulate in 2004, according to the Swedish Security Service.
"The targets have primarily been countries that are participating in the war in Iraq and the Swedish defence industry," it said.
The supermarkets targeted on Thursday were branches of Willys, and Ica and Tempo. The chains are all Swedish, but sell American goods.
Swedish Radio reports that Global Intifada had recently distributed leaflets in Sodertalje encouraging the public to firebomb shops selling American products.
The US embassy in Stockholm has been in contact with the police and has advised people to exercise "caution while shopping and be attentive to suspicious behaviour", Swedish media report.
Sodertalje, an industrial town of 60,000 people, received worldwide attention in recent years after accepting nearly 6,000 Iraqi refugees.