At least 20 people were arrested Monday in the capital Ankara for their suspected links to the Daesh terrorist organization, also known as ISIS, a security source said.

The suspects, all foreign nationals, were arrested in a joint operation by counter-terrorism units of the provincial police department and the Turkish National Intelligence Organization (MIT), said the source, who asked not to be named due to restrictions on speaking to the media.

Read more: Turkey arrests 20 Daesh/ISIS-linked terror suspects