UNITED NATIONS (REUTERS) - US Secretary of State Rex Tillerson said on Friday (Dec 15) that the US government has demanded the release of two Reuters reporters being held in Myanmar.

"Our local representatives at the mission in Myanmar, at the embassy, are expressing our concerns over the detention of individuals, demanding their immediate release or information as to the circumstances around their disappearance," Tillerson told reporters.

Reuters journalists Wa Lone and Kyaw Soe Oo had been working on stories about a military crackdown on the Rohingya Muslim minority in Rahkine State that has caused almost 650,000 people to flee to neighbouring Bangladesh.

They went missing on Tuesday (Dec 12) after being invited to meet police officials over dinner.

Myanmar's information ministry said on Wednesday that the reporters faced charges under the British colonial-era Official Secrets Act, though officials have since said they have not been charged. The 1923 law carries a maximum prison sentence of 14 years.

The reporters "illegally acquired information with the intention to share it with foreign media", said the statement, which was accompanied by a photo of the pair in handcuffs.

They were detained at a police station on the outskirts of Yangon, the South-east Asian nation's main city.

(This story is developing)