'I've raised it with Foreign Minister Zarif,' Kerry told reporters on Thursday at the World Economic Forum in Davos, Switzerland.

'I asked him ... if Iran knew any way to provide help or if there were some way they could have an impact on getting the right kind of outcome,' he added.

'He said he would take that under advisement and try to do what he can. He didn't have any immediate knowledge whatsoever about it,' Kerry added.

According to dispatches, Iraqi authorities are searching for the three Americans, whom the Baghdad security command said were seized last week from a 'suspicious apartment' in south Baghdad, IRNA reported.

Iraqi officials have dubbed the case a kidnapping, but US officials still speak cautiously of a 'disappearance,' in what could become a politically explosive case.

The three were allegedly taken just as Kerry and Zarif were finalizing the implementation of the Iran nuclear deal and the release of five US prisoners held in Iran.

According to the latest reports coming from Baghdad, Iraq's Defense Minister Khaled al-Obaidi said on Thursday the three Americans had been seized by an 'organized gang that carries out abductions for blackmail'.