"We have arrested the perpetrator, a man from Saudi Arabia, a doctor who has been in Germany since 2006," he told reporters, calling the attack a "catastrophe" for the city and the country.
The discovery of the doctor's bloodied body at a government hospital in the eastern city of Kolkata on August 9 sparked nationwide anger at the chronic issue of violence against women.
The outgoing top US diplomat acknowledged that the cleric-run state may be more seriously considering a nuclear weapon after military setbacks in the region.
Cardenas Guillen was captured in 2003 and extradited four years later to the United States, where he pleaded guilty to drug trafficking, money laundering and extortion.
