UNITED NATIONS/YANGON (Reuters) - U.S. Secretary of State Rex Tillerson said on Friday that the United States was demanding  the immediate release  of two Reuters reporters arrested in Myanmar  or information as to the circumstances around their disappearance.  The United States joined mounting demands for the reporters to be freed. The United Nations, United Kingdom, Sweden and Bangladesh, among others, have denounced the arrests. The journalists, Wa Lone, 31, and Kyaw Soe Oo, 27, went missing on Tuesday after being invited to meet police officials over dinner on the northern outskirts of the city of Yangon. They had worked on stories about a military crackdown in Rakhine state, which has triggered the flight of more than 600,000 Rohingya Muslims to Bangladesh since late August. As of Friday, Reuters had not been formally contacted by officials about the detention of the reporters. The Ministry of Information has said that Wa Lone and Kyaw Soe Oo  illegally acquired information with the intention to share it with foreign media,  and released a photo of the pair in handcuffs. Reuters President and Editor-in-Chief Stephen J. Adler has called for the immediate release of the journalists, saying in a statement on Wednesday that the global news organization was  outraged by this blatant attack on press freedom.   A court official in the northern district of Yangon where they were detained said that no paperwork had been filed relating to either journalist. The official said that usually cases are lodged 20-30 days after an arrest as suspects can be held in custody for up to 28 days without being charged. On Wednesday, Myanmar s Ministry of Information said the reporters and two policemen faced charges under the British colonial-era Official Secrets Act, though officials have since disclosed that they have not been charged. The 1923 law carries a maximum prison sentence of 14 years. Last month, the United States called the Myanmar military operation against the Rohingya population  ethnic cleansing  and threatened targeted sanctions against those responsible for what it called  horrendous atrocities.   Tillerson said at the United Nations on Friday that the United States had identified one individual as a sanctions target and was examining others over the campaign in Myanmar against minority Rohingya Muslims. Myanmar s 2-year-old government, led by Nobel Peace Prize laureate Aung San Suu Kyi, has faced heavy international criticism for its response to the Rohingya crisis, though it has no control over the generals with whom it shares power. Rights monitors have accused Myanmar s military of atrocities, including killings, mass rape and arson, against the stateless Rohingya during so-called clearance operations after Rohingya militants  Aug. 25 attacks on 30 police posts and an army base. Amnesty International has called for a comprehensive arms embargo against Myanmar as well as targeted financial sanctions against senior Myanmar military officials. In calling for release of the Reuters reporters on Friday, Tillerson said,  A free press is vital to Myanmar s transition and becoming a viable democracy, and we want Myanmar s democracy to succeed.   He said the U.S. embassy in Myanmar was  expressing our concerns over the detention of individuals, demanding their immediate release or information as to the circumstances around their disappearance.  The embassy said in a statement on its Facebook page on Friday,  We remain concerned about Reuters journalists Wa Lone and Kyaw Soe Oo.   Their families and others have not been allowed to see them, and don t even know where they are being held.  Tillerson s comments came in the wake of a rising chorus of concern in the West over Myanmar s action. The leaders of the U.S. Senate Human Rights Caucus, Republican Thom Tillis and Democrat Chris Coons, said they were  gravely concerned  about the arrests. Earlier on Friday at the United Nations, British Minister for Asia and the Pacific Mark Field said,  We will make it clear in the strongest possible terms that we feel that they need to be released at the earliest possible opportunity.  The nonprofit Committee to Protect Journalists also called for the reporters  unconditional release, saying,  These arrests come amid a widening crackdown which is having a grave impact on the ability of journalists to cover a story of vital global importance.    Swedish Foreign Minister Margot Wallstrom said the arrests were a  threat to a democratic and peaceful development of Myanmar and that region .  We do not accept that journalists are attacked or simply kidnapped or that they disappear,  Wallstrom told reporters on Friday at the United Nations. U.N. Secretary-General Antonio Guterres said on Thursday that the arrests were a signal that press freedom is shrinking in Myanmar and the international community must do all it can to get the reporters released. Britain has expressed  grave concerns  to the government of Myanmar over the arrest of the two journalists, Foreign Secretary Boris Johnson told reporters in London on Thursday.  We are committed to freedom of speech and people s ability to report the facts and bring into the public domain what is happening in Rakhine state,  he said. Bangladesh, which is struggling to cope with the influx of  refugees into its southern tip, also condemned the arrests of reporters working for an agency that had shone a light for the world on the strife in Rakhine state.  We strongly denounce arrests of Reuters journalists and feel that those reporters be free immediately so that they can depict the truth to the world by their reporting,  said Iqbal Sobhan Chowdhury, information adviser to Prime Minister Sheikh Hasina.     In Japan, Prime Minister Shinzo Abe s spokesman Motosada Matano, said his government is closely watching the situation. He said Japan has been conducting a dialogue with the Myanmar government on human rights in Myanmar in general.  