ABOARD THE ADMIRAL ESSEN (AP) — Russia fired a salvo of cruise missiles from the Mediterranean on Thursday and said they struck Islamic State targets in eastern Syria. Activists there said at least 20 civilians were killed in what they described a "fanatical" bombardment — blaming some of it on Russia and some on the United States.

It was not clear whether there was a connection between the Russian military strikes and the activists' accounts, reflecting the challenge of verifying the conflicting claims in the hostile environment of Syria's civil war, now in its seventh year.

The seven Kalibr...