President-elect Donald Trump’s national security adviser and Russia’s ambassador to the U.S. have been in frequent contact in recent weeks, including on the day the Obama administration hit Moscow with sanctions in retaliation for election-related hacking, a senior official said Friday. Trump spokesman Sean Spicer acknowledged contacts between Michael Flynn and Ambassador Sergey Kislyak, but said a phone conversation occurred on Dec. 28, one day before the sanctions were levied.