Russia launched a new aerial bombardment on Syrian rebels, helping President Bashar al-Assad's government reclaim territory it had lost.
On Saturday, spokesman Igor Konashenkov told Russian reporters that the military had increased its number of strikes because of "significant growth in the number of ground targets" detected through aerial and satellite reconnaissance.
Meanwhile, top U.S. and Russian defense officials have held talks via video conference as part of an effort to promote safe operations for the various militaries now flying in increasingly crowded airspace.
U.S. Defense Department spokesman Peter Cook described the talks as "professional" and said they focused narrowly on air safety procedures.
In addition to warplanes from Syria and Russia conducting airstrikes in Syria, the U.S. has been leading a coalition conducting its own strikes, including forces from Australia, Canada, France, Jordan, Britain and the Netherlands.