There is a lot of criminals in Moscow, including uniformed ones. Recently a group of FSB officers (elite Alfa unit) was detained for robbery. About 2 mln Pounds were stolen.And Moscow isn't?
But as for street criminals then Moscow is relatively safe city. The centre is monitored by the police 24/7. It is enough to call 112 and police mobile unit would be on the spot within 2-3 minutes.