Prosecutors in Myanmar have formally charged two Reuters reporters who were covering the country’s Rohingya crisis with violating the Official Secrets Act.

Wa Lone and Kyaw Soe Oo were arrested after police accused them of violating the colonial-era law by acquiring “important secret papers” from two police officers.

The act dates back to 1923, when Myanmar, then known as Burma, was a province of British India.

The Reuters journalists had been invited to meet police officers who worked in Rakhine state, where a harsh military crackdown is blamed for human rights abuses against the Rohingya, which sparked an exodus of 650,000 people to Bangladesh, according to UN estimates.

Bullets and burns: injured Rohingya refugees Show all 10 1 /10 Bullets and burns: injured Rohingya refugees Bullets and burns: injured Rohingya refugees Rohingya refugee Mohamed Jabair, 21, reveals the burns on his bod, which he said he sustained when his house was set on fire in Myanmar REUTERS/Jorge Silva Bullets and burns: injured Rohingya refugees Refugee Momtaz Begum, 30, at Balukhali refugee camp. Begum told how soldiers came to her village demanding valuables.After beating her, they locked her inside her house and set the roof on fire. She escaped to find her three sons dead and her daughter beaten and bleeding REUTERS/Jorge Silva Bullets and burns: injured Rohingya refugees Imam Hossain, 42, sleeps at Kutupalang refugee camp, near Cox's Bazar. Hossain said he was returning home after teaching at a madrassa in his village when three men attacked him with knives REUTERS/Jorge Silva Bullets and burns: injured Rohingya refugees Rohingya refugee Setara Begum, 12, at Nayapara refugee camp. The home of Begum and her siblings was hit by a rocket. The young girl received no treatment for the severe burns to her feet. Her feet healed but she has no toes. Her mother said: 'She has been mute from that day, and doesn't speak to anyone. She only cries silently' REUTERS/Jorge Silva Bullets and burns: injured Rohingya refugees Mohamed Heron, 6, and his brother Mohamed Akter, 4, show the burns on their bodies at Kutupalong refugee camp. The boys' uncle said the burns resulted from Myanmar's armed forces firing rockets at their village Reuters Bullets and burns: injured Rohingya refugees Kalabarow, 50, at Leda refugee camp, in Bangladesh. Kalabarow said her husband, daughter and son were killed when soldiers fired on her village in Maungdaw. She was hit and lay on the floor pretending to be dead for several hours before a grandson found her. During their journey to Bangladesh, a village doctor amputated her REUTERS/Jorge Silva Bullets and burns: injured Rohingya refugees Ansar Allah, 11, at Leda refugee camp in Bangladesh. Allah showed a large scar – the result of a gunshot wound. His mother Samara said: 'They sprayed us with bullets, as our house was burning' REUTERS/Jorge Silva Bullets and burns: injured Rohingya refugees Anwara Begum, 36, at Kutupalang refugee camp, near Cox's Bazar. Begum said she woke to find her home in Maungdaw township in flames REUTERS/Jorge Silva Bullets and burns: injured Rohingya refugees Abdu Rahaman, 73, at Leda refugee camp in Bangladesh. Rahaman, a merchant from Maungdaw, was ambushed while walking on a mountain path with other refugees. A machete thrown at his feet severed three toes REUTERS/Jorge Silva Bullets and burns: injured Rohingya refugees Nur Kamal, 17, described how soldiers assaulted him after they found him hiding in his home in Maungdaw. His uncle found him unconscious in a pool of blood. It took them two weeks to get to Bangladesh. Kamal said: 'We want the international community to help us obtain justice' REUTERS

The government of Myanmar has admitted for the first time that its soldiers had “broken the rules of engagement” in the conflict in north-eastern Rakhine.

After the bodies of 10 Rohingya Muslims were found in a mass grave, a statement on the Facebook page of the country’s armed forces chief admitted members of the security forces – as well as “villagers” – had been involved in the killings.

The statement said 10 “Bengali terrorists” had been killed after “threatening and provoking” Buddhist villagers. The government refuses to use the term Rohingya and calls Muslims in Rakhine “Bengalis” to paint them as illegal immigrants.

Dozens of journalists waited outside court on Wednesday wearing black as a sign of protest against the Reuters reporters’ arrests. Several of their T-shirts said “journalism is not a crime” or “release the arrested journalists now”.

Reuters’ editor-in-chief, Stephen J Adler, said in a statement it was a “wholly unwarranted, blatant attack on press freedom”.

“Our colleagues should be allowed to return to their jobs reporting on events in Myanmar,” he said.

Speaking from the back of a police truck after the brief hearing, Wa Lone said: ”This is unacceptable.

“I want to tell you that they are charging us like this to stop us finding the truth. Their actions are wrong and unfair.”

The two journalists face up to 14 years in prison if convicted, according to their lawyer, Than Zaw Aung.

He appealed for the pair to be immediately released on bail, but the judge said he would review the request and rule at the next hearing on 23 January.

The Ministry of Information had previously cited police saying they were “arrested for possessing important and secret government documents related to Rakhine state and security forces”. The ministry said they “illegally acquired information with the intention to share it with foreign media”.

Drone footage shows thousands of Rohingya Muslims fleeing Myanmar

Human rights and media groups have criticised Myanmar’s leader, Aung San Suu Kyi, a Nobel Peace Prize laureate, for continuing to use colonial-era laws to threaten and imprison journalists.

The events have caused an international outcry, with government officials from the United States, Britain and Canada, as well as top United Nations officials, calling for the journalists’ release.

After they were detained, the UN Secretary General, Antonio Guterres, said the arrests showed how press freedom was deteriorating in Myanmar, while Rex Tillerson, the US Secretary of State, called for their immediate release.

“A free press is critical to a free society – the detention of journalists anywhere is unacceptable,” Bill Clinton, the former US President, tweeted. “The Reuters journalists being held in Myanmar should be released immediately.”

Phil Robertson, a spokesman for Human Rights Watch, said: “If Aung San Suu Kyi and her government really cared about democratic reforms and governance, they could use their parliamentary majority to quickly reform this antiquated colonial law and bring it into compliance with international human rights standards.”

Shawn Crispin, senior South-east Asia representative for the Committee to Protect Journalists, said: “These criminal charges represent a giant step backward for press freedom in Myanmar.

“The jailing of journalists shows that Aung San Suu Kyi’s government, despite its democratic mandate, is following in the repressive footsteps of her military government predecessors. And by targeting a high-profile news organisation like Reuters, it shows no journalist is safe to report on sensitive stories in Myanmar.”