Pillay said she heard allegations of intrusive military involvement in civilian affairs, including education, agriculture and tourism, in the former war zone; the military's acquisition of land from war victims to build bases and even a holiday resort; and sexual harassment of women and girls.
Pillay said that after she visited the former war zone in predominantly Tamil areas in the north and east of the Indian Ocean island nation she heard reports that some of the civilians and rights activists who spoke to her were later questioned by the military or police.
The U.N. considers this "an extremely serious matter," she said.
Pillay's visit followed a resolution in the U.N Human Rights Council in March which called on Sri Lanka to investigate more alleged war crimes committed by government forces and Tamil Tiger rebels. The Tamil Tigers were fighting to create an independent state for ethnic minority Tamils, claiming they faced discrimination from the Sinhalese majority.
A U.N. report has indicated that as many as 40,000 people may have been killed in the final phase of the civil war.
Pillay will report her findings to the council at the end of this month.