Michael Adebowale, the 22-year-old suspected of killing Lee Rigby in a machete attack Woolwich last Wednesday, has been discharged from hospital.
He has now been taken into custody at a south London police station, Scotland Yard said.
In a statement they added: "On arrival at the police station he was further arrested on the suspicion of the attempted murder of a police officer.
"He remains in custody and will be interviewed by detectives from the Metropolitan Police Service Counter Terrorism Command."
Adebowale and Michael Adebolajo were arrested at the scene of the attack last Wednesday.
On Monday, a tenth arrest was made in connection with the murder of soldier Lee Rigby, with a 50-year-old man arrested in Welling, south east London, Scotland Yard said. An address was also searched in south east London.
Earlier, three men arrested on Saturday over Drummer Rigby's killing were released on bail.