"The tribunal ruled that Myanmar is guilty of genocide against the people of Kachin and Muslim groups there," Daniel Feierstein, head of seven-member Permanent Peoples' Tribunal, said.
The Permanent Peoples' Tribunal was founded in Italy in 1979 and comprises 66 international members. Since its establishment, the tribunal has held 43 sessions on numerous cases involving human rights and genocide.
The tribunal, which convened in Malaysian capital Kuala Lampur for five days, took into account various documentaries, expert evidence and testimony of some 200 victims of the atrocities committed against the Rohingya, Kachin and other Muslim minority groups.
It called on the Myanmar government to put an end to the violence against Muslim minorities.
"Visas and free access must be granted to the United Nation's Fact Finding to probe the atrocities committed against the Rohingya, Kachin and other groups in Myanmar," the tribunal said in a statement.
It said the government must amend its constitution and abolish discriminatory laws to give rights and citizenship to the oppressed minorities.
Since Aug. 25, some 429,000 Rohingya have crossed from Myanmar's western state of Rakhine into Bangladesh, according to the UN.
The refugees are fleeing a fresh security operation in which security forces and Buddhist mobs have killed men, women and children, looted homes and torched Rohingya villages. According to Bangladeshi Foreign Minister Abul Hasan Mahmood Ali, around 3,000 Rohingya have been killed in the crackdown.
The tribunal also called on the international community to provide financial help to countries such as Bangladesh and Malaysia that are hosting the influx of refugees escaping the violence.
Malaysia currently hosts one of the largest urban refugee populations in the world. As of 2014, some 146,020 refugees and asylum seekers had been registered with the UNHCR in Malaysia, of which the vast majority or some 135,000 are from Myanmar.
The Rohingya, described by the UN as the world's most persecuted people, have faced heightened fears of attack since dozens were killed in communal violence in 2012.
Last October, following attacks on border posts in Rakhine's Maungdaw district, security forces launched a five-month crackdown in which, according to Rohingya groups, around 400 people were killed.
The UN documented mass gang rapes, killings -- including of infants and young children -- brutal beatings, and disappearances committed by security personnel. In a report, UN investigators said such violations may have constituted crimes against humanity.