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WASHINGTON (AFP) - The US embassy in Stockholm has boosted security following an unspecified threat and Sweden's first suicide bombing, the embassy said on its website.

"In response to a threat against the US Embassy, Stockholm, please be advised that the embassy has enhanced its security posture," according to a message posted Monday on the embassy's website.

"In light of last week’s suicide bombing and the increased threat level in Sweden, we think it prudent and necessary to take these additional precautions," it said.

On December 11, a man blew himself up near a busy pedestrian street in Stockholm, killing only himself in Sweden's first suicide bombing. But two people were injured when his car exploded nearby minutes earlier.

Reports have said suspect Taimour Abdulwahab, a Swedish citizen, arrived in Sweden as a child from Iraq, and could have become radicalized in Britain, where he attended university and lived for the last few years.

The bomber sent an email to Swedish news agency TT and to intelligence agency Saepo before the twin blasts, in which he told "all hidden mujaheddin in Europe, and especially in Sweden, it is now the time to fight back."

"The Islamic State, may Allah protect it, and its people, have now begun to fulfill its promises," he said in an English-language audio-file attached to the email.

"No more oppression against Islam or Muslims will be tolerated in any way or any means," he said, speaking specifically of Swedish artist Lars Vilks' drawing of the Prophet Mohammed as a dog and of Swedish troops deployed in Afghanistan.

The US embassy said it will remain open for services and maintain normal business hours. It added that its consular section also will remain open for all services.