Police probe Stockholm blasts as act of terrorism

STOCKHOLM (Reuters) - Police said on Sunday they were investigating two bomb blasts in Stockholm as an act of terrorism after an emailed threat over Sweden's troops in Afghanistan.

Police stopped short of saying Saturday afternoon's blasts, which killed the suspected bomber and wounded two people, were a suicide attack. A car blew up in a busy shopping area, followed minutes later by a second explosion nearby.

Shortly before the blasts, Swedish news agency TT received a threatening letter referring to Sweden's presence in Afghanistan and caricatures of the Prophet Mohammad drawn by a Swedish cartoonist. The letter included digital sound files with a recording in broken Swedish and in Arabic.

The incident follows several nervous months in Europe after a U.S. travel alert about possible attacks by militants and a failed bid by a Yemen-based al Qaeda group to use air cargo to send parcel bombs via Europe to America.

German authorities last month said they were on guard against threats of armed attack on civilians of the kind that killed 166 in the Indian city of Mumbai in 2008.

TT said the letter promised attacks over Sweden's presence in Afghanistan where it has 500 troops with the U.S.-led NATO force and the caricatures drawn three years ago by Swedish artist Lars Vilks.

"This is a very serious incident, which is being investigated as an act of terrorism," Anders Thornberg, director of operations at the Security Police, said in a statement.

The police declined to go into further detail about the dead man's motives or speak about his identity.

Swedish broadcaster SVT, citing unidentified sources, said the dead man was thought to be a 29-year-old from the small town of Tranas, about 200 km (124 miles) southwest of Stockholm.

"As far as we know, it looks like he was working for himself, but we have to be really sure so we are investigating that there could be more perpetrators," Thornberg told Reuters.

Daily Aftonbladet on Saturday quoted a source as saying the man was carrying six pipebombs, of which one exploded, and a rucksack full of nails and suspected explosive material.

The police would not comment.

WORRIED EUROPE

Sweden did not raise its security threat level -- currently at "elevated," two notches below the top level -- but police stepped up their presence in Stockholm.

Britain, which has been targeted by similar attacks, said it was in touch with Sweden.

"Other European capitals must be worried about the fact that this happened in a capital city in the run-up to Christmas," said Claude Moniquet, head of the European Strategic Intelligence and Security Centre think-tank in Brussels.

"It could be a signal to other potential attackers to prompt them to attack at this time."

Evan Kohlmann, a U.S. terrorism consultant, said he suspected the attack was "a home-grown local extremist who may or may not have connections to any actual terrorist organisation."

Prime Minister Fredrik Reinfeldt urged Swedes to remain calm and not let their belief in tolerance and openness be shaken. "We cherish this society. This society is worth defending," he said.

Police arrested a man who was spotted getting out of a car brandishing an axe near the prime minister's office just before Reinfeldt spoke.

The Islamic Association in Sweden condemned the blasts. "The attack is a shock to us all, and strikes at our joint peace and security," Chairman Omar Mustafa said in statement.

RETURN TO CALM

There was little evidence that Stockholmers were deterred from their holiday shopping.

"Of course these things can happen in Sweden ... but it feels surreal. It's too close," said Cecilia Hermansson, a young Swedish woman visiting Stockholm for a course.

The incident began when a car burst into flames near a busy shopping street in the city centre, followed by explosions inside the car which police said were caused by gas canisters.

The second explosion, about 300 metres (yards) away and 10-15 minutes later, killed one man and wounded two people.

Newspaper Dagens Nyheter quoted a medic as saying after the second blast that the dead man had been carrying something that exploded in his stomach. The paper quoted witnesses as saying the man was shouting in what was apparently Arabic.

TT said the email it received was also sent to the Security Police. "Our actions will speak for themselves, as long as you do not end your war against Islam and humiliation of the Prophet and your stupid support for the pig Vilks," TT quoted a man as saying in one recording.

Vilks depicted the Prophet with the body of a dog. Many Muslims consider any image of the founder of Islam offensive.

In March, an American calling herself "JihadJane" was charged with plotting to kill Vilks. In May, arsonists tried to set fire to his house.

(Additional reporting by William Maclean, Ilze Filks and Niklas Pollard; Writing by Adam Cox and Patrick Lannin; Editing by Janet Lawrence)