Myanmar’s military junta has appeared in place of the detained Aung San Suu Kyi at the UN’s top court, where it sought to throw out a case alleging that it committed genocide against the country’s Rohingya minority.

The decision to allow the junta to represent the country in court, after it seized power in a coup last year, was strongly criticised by advocacy groups and a former UN special rapporteur, who warned that it risked delaying justice.

The claim that Myanmar’s military carried out genocide was brought to the international court of justice (ICJ) by the Gambia after a brutal 2017 military crackdown that forced an estimated 700,000 Rohingya to flee over the border to neighbouring Bangladesh. UN investigators have since alleged the military’s operations were carried out with “genocidal intent”.

Previously, Aung San Suu Kyi travelled to the court to defend Myanmar against claims the military carried out mass murder, rape and destruction of Rohingya Muslim communities. She is now being held in detention at the behest of the military, which seized power in February 2021 and charged her with a raft of offences.

Aung San Suu Kyi was replaced in court by the junta’s minister of international cooperation, Ko Ko Hlaing, and its attorney general, Thida Oo. Both are subject to US sanctions prompted by the military’s use of brutal violence to repress opposition to the coup.

The national unity government (NUG), formed by elected lawmakers, ethnic minority representatives and activists, had said it intended to represent Myanmar at the ICJ. It said it had withdrawn preliminary objections – unlike the junta, whose representatives argued on Monday that the Gambia did not have the legal right to file the case.

Yanghee Lee, a former UN special rapporteur on human rights in Myanmar, called the hearings a disgrace. “The court should instead recognise the NUG’s authority, formally dismiss the objections, and move swiftly to dealing with the actual substance of the case, the atrocities against the Rohingya people.”

The junta’s lawyers outlined several objections, including claims that the Gambia was acting as a “proxy” for the Organisation of Islamic Cooperation, and therefore lacked standing because the ICJ only rules on disputes between states.

Ko Ko Hlaing told the court that the junta, which he referred to as the government of Myanmar, was determined to solve the problems in Rakhine state “through peaceful means of negotiation and reconciliation”.

Rights groups point out that the military is in the midst of a deadly campaign of violence against the public. Over the past year alone, in the aftermath of the coup, its has torched villages, massacred civilians and carried out airstrikes across the country to silence opposition.

Tun Khin, president of the Burmese Rohingya Organisation UK, said the military had totally failed to comply with a previous order issued by the court, which said Myanmar must prevent genocidal violence against Rohingya and preserve any evidence of past crimes.

“The Rohingya in Myanmar today are subjected to daily harassment and intimidation by authorities, while there are also state-enforced restrictions on their movement, as well as their access to healthcare, education and livelihoods,” Tun Khin said.

The junta was also blocking humanitarian assistance, leaving many Rohingya on the brink of starvation, he added.

A representative of the Rohingya Student Network, who spoke from Cox’s Bazar in Bangladesh, told the Guardian the ICJ case represented not only the prospect of justice for Rohingya people, but also the “hope to bring a federal democracy in Myanmar for all those who are fighting [for an end to military rule] in Myanmar right now”.

The military’s seizure of power has prompted a shift in attitudes towards minorities. Previously there was little solidarity with Rohingya, but since the coup some protesters have apologised for not standing by Rohingya or believing their claims of persecution.

“They joined our fight from 1 February,” said the Rohingya activist, who asked not to be named due to security concerns, referring to the date of last year’s coup. “They just joined our fight, that we [have been] fighting for decades.”

Akila Radhakrishnan, president of the Global Justice Centre, said she did not believe the junta’s appearance before the court would lend legitimacy to the military. It was likely to simply reflect a continuation of the status quo in court procedures, she said.

Radhakrishnan added: “There is such a strong link between impunity and the coup occurring, and the fact that the military has very rarely faced any direct consequences, that I think there is import to the fact that they are learning that they will be hauled into court – and this time around, unlike 2019, they can’t hide behind Aung San Suu Kyi and the civilian government.”