The men were seized under the Terrorism Act at two separate properties in Tooting in south London.
Police said six of the men were arrested at one property and three at another before being taken to a central London police station.
Britain’s Press Association said it is not thought any of them are the three bombers believed still to be on the run.
Hours earlier, police arrested three women on suspicion of harbouring offenders in a raid linked to the same bombings.
Their arrest came within hours of the capture of a suspected bomber accused of trying to carry out a suicide bombing during the second wave of attacks.
The women were seized after a raid in Stockwell in south London, close to the underground train station where a Brazilian man was mistakenly shot dead by police last Friday.
“The arrests are in connection with the ongoing investigation into the attacks on July 21,” a London police spokeswoman said.
She declined to give further details.
Witnesses told Reuters police armed with automatic weapons and shotguns handcuffed the women before taking them away.
The attempted bombings on July 21 came two weeks after four suicide bombers killed 52 people in three underground trains and a bus.
Earlier, police arrested bombing suspect Yasin Hassan Omar, 24, in Birmingham using a stun gun.
The Somali-born man’s picture was captured on closed circuit television leaving one of the London Underground stations after the attempted attack.
Metropolitan Police anti-terrorism chief Peter Clarke says Omar was arrested alone during a pre-dawn raid in a house in the central England city of Birmingham.
Mr Clarke says police are still looking for the three other suspects.
“I must emphasise that until these men are arrested they remain a threat,” he said.
Hassan Omar is among four men suspected of having tried but failed to blow up three London trains and a bus on July 21, in attacks mirroring the July 7 bombings that killed 56 people.