Sweden's military is investigating a major security breach after a member of staff left a memory stick holding classified data on a public computer.
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The story was reported by Aftonbladet newspaper, which was given the device by a member of the public who found it at a computer centre in Stockholm.
The paper returned the stick, which the military said included information on security threats in Afghanistan.
A military spokesman said the incident was being taken very seriously.
"It's primarily a matter of security for our soldiers," said Colonel Bengt Sandstrom of the Military Intelligence and Security Service (Must) in a statement.
"This is also a serious matter from a legal standpoint. Carelessness with regards to classified information is an offence that is punishable by up to six months in prison."
The statement said an employee had acknowledged the loss of the chip to his superiors.
The memory stick - a removable device for holding computer data, about the size of a key - contained documents about improvised explosive devices and mines in Afghanistan, as well as information about other countries including the US. Some of the data was classified.
Must is currently analysing the contents of the stick to assess the possible damage that the incident could have caused, the statement said.
Col Sandstrom was due to meet military attaches of the countries concerned to discuss the incident, it added.