Aung San Suu Kyi, the detained Burmese pro-democracy leader, could be released by the country's military rulers later today, according to reports and supporters.

The 65-year-old's latest 18-month term of house arrest ends tomorrow, and there are reports in Rangoon that she might be freed as early as this afternoon, campaigners say. The Nobel peace laureate has been detained for 15 of the past 21 years.

The BBC cited sources in Burma as confirming that documents authorising her release had been signed. A spokesman for the Burma Campaign UK said he had heard similar reports.

"There are rumours that the police are outside her house and could be delivering documents connected to her freedom. However, we really don't know. If there are conditions attached to her release she might not agree to it," he said.

Aung San Suu Kyi's lawyer, U Nyan Win, has previously said that she will not accept conditions, for example not being allowed to travel freely around Burma.

Other reports were more definite about imminent news. "The authorities will release her. It is certain," AFP quoted an unnamed Burmese government official as saying. "She will be released for sure as planned," another official told the same news agency.

Aung San Suu Kyi's National League for Democracy (NLD) won a landslide victory in 1990 elections but the country's military rulers simply ignored the result and repeatedly sentenced her to periods of detention at her home in Rangoon. Her latest period of house arrest was extended for 18 months after a US tourist swam unannounced across a lake to the rear of her property on what he described as a mission to "save" her.

Burma's first elections since 1990 were held on Sunday, but they were widely dismissed by outside observers as a sham. Results published yesterday showed that the main military-backed party, the Union Solidarity and Development party (USDP), had won 190 of 219 seats so far declared in the lower house and 95 of 107 seats in the upper chamber.

The NLD refused to take part and was ordered to disband by the government.