TOKYO: Myanmar must have peace to carry out sustainable development, leader Aung San Suu Kyi said on Friday, as human rights activists say conflict in the north of the troubled state of Rakhine has led to civilian abuse by the military.

Nobel Peace Prize winner Suu Kyi is in Japan on a five-day visit to court investment and aid, as an upsurge in violence against the persecuted Muslim minority Rohingya at home poses the worst crisis of her six months in power.

She has faced mounting criticism abroad for her government's handling of the crisis in Rakhine, where soldiers are accused of raping and killing civilians and where aid workers were refused access until the government on Thursday agreed to allow such work to resume.

The violence is the most serious to hit Rakhine since hundreds were killed in communal clashes in 2012.

But tension between Myanmar's ethnic minorities and the majority Burmans has prompted many groups to take up arms and fight the military on the fringes of the country since independence in 1948.

"We are still not at peace, there is still armed conflict between various ethnic groups in our country," Suu Kyi told Japanese business leaders. "We must have peace in order that our development may be stable and sustainable."

She gave no further details.

Suu Kyi has not directly commented on calls from human rights experts urging the government to investigate the allegations of abuse in Rakhine, or on statements from human rights monitors, although she has urged the military to act with restraint.

"We want all our ethnic peoples to feel that they have an equal chance to progress, that it is truly a nation made up of diverse peoples but united in our purpose to be a society that is at harmony," she told the business leaders.

The Rakhine military operation has sharpened the tension between Suu Kyi's six-month-old civilian administration and the army, which ruled the country for decades and retains key powers, including control of ministries responsible for security.

While Myanmar's army-drafted constitution puts the military firmly in control of security matters, diplomats and aid workers say privately they are dismayed at Suu Kyi's lack of deeper involvement in the handling of the crisis that has included a string of foreign trips as the crisis deepened.