"We view this as a wholly unwarranted, blatant attack on press freedom", said Reuters Editor-in-Chief Stephen J. Adler.
Wa Lone and Kyaw Soe Oo, who have both been covering the crisis in Rakhine State for Reuters, were arrested on December 12 after meeting with police officers in Yangon.
Their families have suggested the pair were set up, saying the arrests took place immediately after leaving the restaurant where they dined with the two policemen.
Over 656,000 Rohingya refugees, mostly children and women, have fled Bangladesh since Aug 25, when Myanmar's forces launched a crackdown on the minority Muslim community in Rakhine state, according to the UN.
Before a Yangon district judge Wednesday, government prosecutors sought charges against the journalists under Section 3.1 (C) of the Official Secrets Act, a 1923 law made to deter espionage against British colonial rule.
The section punishes anyone who "obtains, collects, records or publishes. any official document or information" which could be "useful to an enemy".
In a report released in November, Fortify Rights and the United States Holocaust Memorial Museum found "mounting evidence" of the crime of genocide by state security forces against Rohingya in Rakhine State and documented information about mass graves. An information ministry bulletin at the time of their arrest said they had "illegally acquired information with the intention to share it with foreign media".
"We applied for bail but the prosecutors rejected it", the journalists' lawyer Khin Maung Zaw told AFP. The court took it under consideration and will decide at the next hearing on January 23, he said. When they went outside, seven police surrounded them and arrested them.
About 30 journalists were outside the court, most dressed in black as a sign of protest against the arrest of the pair.
The same month as their release, prominent journalist Ko Swe Win was arrested at Yangon Airport on suspicion of violating the notorious clause 66 (d) of the Telecommunications Act, which covers online defamation, for a Facebook post deemed critical of nationalist monk U Wirathu.
In all cases, after protracted trials, charges were eventually dropped, indicating a pattern that many hope will hold for Wa Lone and Kyaw Soe Oo.
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His colleague Wa Lone said his wife was pregnant, adding: "I'm trying to be strong".
The defence lawyer for two Reuters journalists facing lengthy prison terms has disputed the prosecution's version of events leading up to their arrest.
Emotive scenes gripped the Yangon courthouse with the journalists' family members in tears and the reporters issuing desperate pleas before being led back to detention.
A spokesman for the military was not available for comment.
United Nations Secretary General António Guterres, United States Secretary of State Rex Tillerson, and other government officials internationally have also called for the release of Wa Lone and Kyaw Soe Oo.
Observers from the United Nations and from several embassies, including the Netherlands, Australia and Britain were at the court.
The U.S. said it was "deeply disappointed" by Myanmar's decision to pursue charges. The same month, three journalists from local outlets, The Irrawaddy and Democratic Voice of Burma, were arrested for making contact with an ethnic armed group in Shan State. "We call for their immediate release", it said in a statement.
Human rights group Amnesty International also called for their immediate release and for freedom of speech to be respected. Authorities have largely banned media from the conflict zone.
Former US president Bill Clinton has urged that the journalists be freed immediately.
Ever since the Rohingya refugee exodus began in late August, journalists have been systematically denied access to the region, an issue that RSF raised with Myanmar's leader, Aung San Suu Kyi, in September.
Suu Kyi won a 2015 election and formed a government in early 2016, although she is barred by the constitution from becoming president.