The US has added Nigeria to a list of countries for which Washington is especially concerned about threats to religious freedom.

The Secretary of State, Mike Pompeo, didn't give the reasons for the decision as he announced it, but a State Department report earlier this year pointed to mass detentions of members of a NIgerian Shia group and the arrests in one state of Muslims who were ignoring Ramadan fasting rules.

The US list also includes China, Iran, Pakistan, Myanmar, North Korea and Saudi Arabia.

Countries on the list can face US sanctions if they fail to improve their records on religious freedom.