"The court should discontinue the current hearing and proceed to the merits. The court can play a powerful role for Myanmar," Zin Mar Aung said by video link.
She called on the international community to support the Rohingya and "not allow the military ... this platform".
The court had determined the hearing could proceed under its rules, on the basis of communications with junta-approved diplomats. Read full story
Monday is the first of four days of the hearing discussing Myanmar's preliminary objections to the case, including whether the ICJ has jurisdiction, a decision that could take months to reach.
The case was brought in 2019 by Gambia, a predominantly Muslim African country, backed by the 57-nation Organisation for Islamic Cooperation.
Gambia sued Myanmar for alleged violation of the Genocide Convention, citing events in 2017 when more than 730,000 Rohingya Muslims fled Myanmar into neighbouring Bangladesh after a military-led crackdown. A UN fact-finding mission concluded that the military campaign had included "genocidal acts".
The Myanmar military denies the accusation, saying it was conducting a legitimate campaign against insurgents who attacked police posts.
Myanmar civilian leader Aung San Suu Kyi attended preliminary hearings in the case in 2019 in the Hague when she also denied genocide had taken place. She has been in detention in Myanmar since the coup.
In a 2020 decision, the court ordered Myanmar to take measures to protect the Rohingya from harm, given the urgency of the matter.
Speaking to reporters outside the court, Ambia Perveen of the European Rohingya Council said that while the junta does not represent the people of Myanmar it was important the case moved ahead.
"The people who perpetrated genocide should be brought to justice," she said.
She said abuses against Rohingya in Myanmar continue while those in camps in Bangladesh live "a life of indefinite uncertainty".
Should the court rule that it has jurisdiction to hear the case, a decision on the merits of Gambia's allegation could take years more to reach.