The ILO has been at loggerheads with Burma for more than a decade over what the United Nations agency calls a widespread practice of forcing villagers to work on infrastructure projects or as porters for the army.
It is also concerned about the recruitment of minors into military service in the secretive state whose ruling junta has been heavily criticized by the West for its reluctance to let in foreign aid workers following Cyclone Nargis, which struck on May 2 and left 134,000 people dead or missing.
As Burma seeks to recover from the devastating storm, the ILO said UN agencies and relief workers must be aware of "the increased risk of incidences of forced labour, child labour, human trafficking and migrant labour as the authorities and individuals come to grips with the sheer size of the tragedy."
The ILO is working with Burmese authorities to "ensure that the reconstruction effort does not involve the use of forced labour in any of its forms," it said in a report on Friday.
Steve Marshall, ILO's liaison officer in Rangoon, submitted the report to the annual International Labour Conference, being held in Geneva through June 13. A key committee of ILO's 182 member states held a debate on Burma on Saturday.
"From the ILO's perspective it is important to assist communities but the reconstruction work must be done in line with international standards," Marshall told Reuters on Friday.
So far, there have not been any verified reports of forced labor linked to the disaster, he said, adding: "We're not saying it isn't happening."
Burma passed a decree in October 2000 abolishing forced labor, which is banned under an ILO Convention it has ratified. The Geneva-based agency was allowed to open an office there two years later to help it eradicate the practice.
But the ILO said in its report some victims of forced labor were harassed or detained in the past year when they sought to report abuses. This had discouraged many others from coming forward and distorted official figures.
Some 89 allegations of forced labor have been lodged under a complaints mechanism set up in February 2007, the report said.
"The incidence of harassment and detention of persons associated with its application has severely limited its operation," it said of the mechanism. "The number of complaints therefore cannot be seen to reflect the size of the issue."
Six young labor activists, sentenced to between 20 and 28 years in jail last year for helping organize a May Day workers' rights seminar, remain in prison, the ILO report said.