Rights groups and the U.S. State Department are continuing to call for Iran to release four people arrested last week, including Washington Post Tehran correspondent Jason Rezaian and two other journalists.
Human Rights Watch said Tuesday that Iran should let them go immediately unless the government plans "recognizable charges" and guarantees them fair trials.
Rezaian is a dual citizen of the United States and Iran. His wife, Yeganeh Salehi, is an Iranian citizen and correspondent for a newspaper based in the United Arab Emirates, while the other two people arrested are U.S. citizens.
U.S. State Department spokeswoman Jen Psaki told reporters Monday that the U.S. is "concerned" about the situation, and that Iran should release them immediately.
Paris-based Reporters Without Borders highlighted the case in discussing the 65 reporters currently jailed in Iran, including 10 women, saying Iran leads the world in the number of imprisoned female journalists.
The group said in a statement Monday it is "extremely concerned" about what it called a wave of arrests aimed at women working in the media.
An Iranian official said last week that Rezaian had been detained for questioning, but did not elaborate.
The Washington Post Executive Editor Martin Baron said the paper was "mystified" and "deeply concerned" about the arrest.