Explosions hit London's subway, bus networks

A number of explosions struck London's Underground subway system during the morning commute Thursday, with at least one aboveground bus also hit with a blast, CNN reported.

Multiple injuries were reported, but there was no immediate estimate as to the extent of the casualties. The cause of the blasts was not immediately known, according to the news channel. The Underground system was shut down, according to CNN.

CNN also reported that London mobile phone networks were overloaded as people tried to alert friends and relatives as to their whereabouts.