An American reporter for the Washington Post and his wife have been detained in Tehran, an Iranian official confirmed.
Jason Rezaian, a 38-year-old dual Iran-US citizen, and his Iranian wife Yeganeh Salehi, were taken into custody on Tuesday evening, the paper said. Two freelance photographers, also US citizens, were being held too.
Western news organisations, including the BBC, have great difficulty operating in Iran, with journalists facing detention and surveillance.
"We are deeply troubled by this news and are concerned for the welfare of Jason, Yeganeh and two others said to have been detained with them," Washington Post foreign editor Douglas Jehl said in a statement.
Mr Rezaian, who is from California, has been the Post's Iran correspondent since 2012. Ms Salehi works as a correspondent for the National, an English-language newspaper based in the United Arab Emirates.
Their detention was confirmed by Iran's Chief Justice Gholamhossein Esmaili, who said they were being questioned but did not give a reason for the arrests, the official Islamic Republic News Agency reported.