WASHINGTON — For the first time since it began military operations in Syria, the Russian government alerted the United States of planned airstrikes, Defense Department spokesperson Peter Cook said Tuesday.

Cook also said the Russian airstrikes were concentrated on targets from the Islamic State group, best known as ISIL or ISIS. That is a change from Pentagon statements in the past, which have identified the vast majority of Russian strikes as attacking non-ISIS forces aligned against the government of Syrian president Bashar al Assad.

"In this instance, their most recent airstrikes, [Russia] did give us advanced notice through the memorandum of understanding that is in place," Cook told reporters.

Russia appears to have launched a wave of new strikes in Syria over the last 24 hours, including cruise missiles and the first ever use of the Tu-160 strategic bombers in combat operations.

The US and Russia reached an agreement on deconfliction in October, but details on the agreement have been kept quiet, something the US said was at the behest of the Kremlin. This is the first time Russia has communicated directly to the US about incoming strikes, however.

Earlier Tuesday, Russian officials confirmed that a bomb was responsible for the Oct. 31 downing of Metrojet Flight 9268 over Sinai, Egypt, which killed everyone on board. ISIL has claimed responsibility for that attack and has threatened further actions against Russia, the US and Europe.

Asked whether the focus of the strikes being on ISIL could present an opening for future collaboration between Russia and the US, Cook reiterated the Pentagon's position that Russia must first act to find a political solution to removing Assad.

Cook also pushed back at the idea that the US has fallen behind Russia in terms of strikes, insisting that "the notion we are behind the curve here is a mistaken one."

Airpower advocates, as well as members of Congress, have criticized what they call a slow pace of airstrikes from the US. The Pentagon says it has launched around 8,000 airstrikes since the anti-ISIS campaign began 14 months ago; Russian officials have claimed a significantly higher pace in its two months of operations.

Later on in the news conference, there appeared to be confusion about a statement from Secretary of State John Kerry about plans to help Turkey secure its border with Syria.

"The entire border of northern Syria – 75 percent of it has now been shut off," Kerry told CNN in an interview, as quoted by Reuters. "And we are entering an operation with the Turks to shut off the other remaining 98 km."

Cook, however, professed to have no knowledge of those operations, and could not say if DoD personnel would be involved.

Turkey has expressed concern over the border. In September, it expressed an interest in new border security equipment, with one Turkish official telling Defense News the country plans to spend "hundreds of millions of dollars on this in the next few years."

Twitter: @AaronMehta