For the first time in history (at least publicly known) two satellites collided in Space. This space accident was happening 485miles over Siberia already on Tuesday.
The US satellite is owned by Satellite phone service provider Iridium. The Russian satellite is said to be not in use anymore.
The crash generated a huge cloud of debris and it is expected to take weeks until the "dust settles" again. NASA says that there is no risk to the ISS right now. Space agencies are tracking the debris of the satellite crash and hope most of it burns in the earth atmosphere.
The orbit around earth is already pretty full with satellites and with debris. At some point they really need to clean up.
More details on BBC News and Reuters. See also the Iridium site.