News reports, citing unidentified sources, said the alleged plot was to kidnap, torture and behead a Muslim British soldier.
West Midlands Police say they have completed searches of 18 properties raided last week, the AP reports.
The suspects, detained on suspicion of the commission, instigation or preparation of acts of terrorism, are being held in Coventry in central England.
Eight of the suspects were arrested in early-morning raids on Wednesday, and the ninth was arrested later in the day.
The discovery of the submarine has unveiled a few "inconsistencies." For example, how can one explain the fact that the sub was found where it needed to be searched for from the start?
This problem is not limited to the situation with the "whale prison" in Russia's Far East, because many people buy tickets to go to oceanariums and turn a blind eye to the problem