Amid “growing reports and photographic evidence” that live ammunition is being used against anti-junta protesters in Myanmar, a United Nations human rights investigator is calling on the Security Council to consider sanctions against the country’s coup leaders.

Thomas Andrews’ remarks at a special session of the U.N. Human Rights Council in Geneva come a day after the U.S. imposed its own sanctions on the generals who overthrew the government of Aung San Suu Kyi on Feb. 1.

Andrews, a special rapporteur for Myanmar, also known as Burma, said that in similar circumstances in the past, the Security Council had “mandated sanctions, arms embargoes, and travel bans” and called for “judicial action at the International Criminal Court or ad hoc tribunals.”

“All of these options should be on the table,” he said, adding that “growing reports and photographic evidence” pointed to the use of live ammunition against protesters.

A letter signed by some 300 elected parliamentarians in Myanmar that was read out at the Geneva forum urged the U.N. to investigate “gross human rights violations” committed by the military since the coup, and said the new authoritarian regime had “placed restrictions on people’s freedom of speech by preparing a telecommunications bill intended to control access to the Internet and mobile services.”

However, the prospects for U.N. sanctions to mirror those imposed by the Biden administration this week appeared dim, with China and Russia – both veto-wielding Security Council members — having signaled their unwillingness to go along with such a move.

President Biden and Chinese leader Xi Jinping discussed the situation in Myanmar during a broad-ranging two-hour phone call on Wednesday, according to the White House.

The U.K. has said it is considering its own sanctions and European Union lawmakers have also called for action.

Nada al-Nashif, the deputy U.N. high commissioner for human rights, called the arrest of Suu Kyi and President U Win Myint and hundreds of others by the country’s coup leaders “politically motivated.”

In a letter to the council, Al-Nashif said her office had tracked “more than 350 political and state officials, activists and civil society members, including journalists, monks and students, who have been taken into custody.”

“Several face criminal charges on dubious grounds. Most have received no form of due process and have not been permitted legal representation, family visitations or communication,” she said.

Suu Kyi, who spent 15 years under house arrest at the hands of previous military governments, was detained following this month’s coup on charges of illegally importing walkie-talkies.

Meanwhile, in Myanmar on Friday, hundreds of thousands of pro-democracy demonstrators turned out to defy the junta. Some supporters of Suu Kyi clashed with security forces, Reuters reports. At least three people were wounded in the southeastern city of Mawlamyine when police opened fire with rubber bullets, a Myanmar Red Cross official told the news agency.