The Armed Forces have alerted the Swedish Security Service (Säpo) about the missing documents, which disappeared during the 2006 closing of the F4 air wing in Östersund in northwestern Sweden, according to the Dagens Nyheter (DN) newspaper.

Citing sources familiar with the situation, the newspaper reports that Säpo’s counterespionage unit was informed about the missing documents last Wednesday.

The documents included a list of secret defence facilities located throughout the northern Sweden and covering more than 50 percent of country’s territory.

In addition to the locations of simple defence fortifications, the list also included the locations of secret command centres.

It remains unclear whether the documents, which were created in 2003, have been destroyed or fallen into the hands of a foreign power, DN reports.

According to the Armed Forces, exposure of the information in the documents would constitute “a not insignificant injury to the country’s defence and the nation’s security”.

“I can’t comment on the information because I haven’t had a chance to verify the information,” said Daniel Ström, deputy head of the Armed Forces legal department, to the TT news agency.

He emphasized, however, that the missing documents were not classified as secret, a higher degree of classification.

“I have a hard time believing that it involved documents which qualify as secret documents,” said Ström.