"The suspects, who are not a family group and were not accompanied by children, did not pose any immediate risk to public safety," West Midlands Police said on Twitter Friday.
The arrests are a part of an ongoing investigation, according to the police.
The detainees, all in their 20s, were taken into custody in central England. Police are conducting searches in the city of Birmingham, where four suspects lived.
Earlier this week, nine British nationals were arrested in Turkey after trying to illegally cross the Syrian border. The group comprised the son of a Labour councilor and his family. They are expected to be deported to the United Kingdom on Saturday.
Many European citizens, including British nationals, have recently travelled to Syria and Iraq to join extremist groups, such as Islamic State (ISIL). The jihadist group’s intensive propaganda efforts on social networking websites especially target young people.
According the International Centre for the Study of Radicalisation and Political Violence, up to 600 Britons have joined militant groups in Iraq and Syria.