The burglary is not thought to have been politically motivated

The documents were in a briefcase taken during the burglary in Estonia's second city, Tartu, last week, but Mr Hanson did not tell the police until Monday.

Estonia was among seven former communist eastern European countries to join Nato in March.

It has not been revealed what the stolen papers contained.

Mr Hanson said that he did not think he could continue as a minister, given the circumstances.

"I could not foresee there would be burglars in my house," he said. "As a rule, I don't take work-related information home, but my tight schedule lately unfortunately did not allow me to abide by this rule.

"But stepping down in this situation is suitable for the minister of a Nato country."

His Reform Party, which had been due to discuss sacking him, has not yet named a replacement.

State authorities have launched an investigation into the burglary, which is not thought to have been politically motivated.

According to Estonian law, the punishment for unintentional negligence in handling state secrets can range from minor charges to a year in prison.