U.S. and Russian aircraft come within visual range over Syria

Two Russian and two U.S. aircraft came within visual range of each other -- separated by just 10 to 20 miles -- over Syria Saturday, according to the anti-ISIS coalition.

Both sets of aircraft moved away and there was no incident, said Col. Steve Warren, spokesman for the U.S.-led coalition, Tuesday. "Everyone went about their business."

Yet Warren called Russian airstrikes in Syria "reckless and indiscriminate" as well as "irresponsible."

Russian aircraft are also continuing to shadow U.S. drones.

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Of the 80 airstrikes the U.S. believes the Russians have conducted, "only a fraction" are against ISIS targets, Warren said.

Russian airstrikes have had no demonstrated progress yet strengthening the regime of Syrian President Bashar al-Assad, according to Warren.

Russia acknowledged Monday that its airstrikes are intended to help the Syrian President, a close ally, but Moscow has also insisted that most of its targets have been terror groups, including ISIS.

In defending the U.S. air campaign, Warren said 70 senior and mid-level ISIS leaders have been killed by U.S. airstrikes since May, forcing the group to constantly replace that leadership.

He reiterated U.S. assessments that ISIS has become increasingly paranoid about its operational security to keep leaders safe from airstrikes.