U.S. President Donald Trump's national security adviser, Michael Flynn, has resigned. He admitted that he gave incomplete information on contacts with the Russian Ambassador Sergei Kislyak at the end of December and apologized to Donald Trump.  Lt Gen Joseph Keith Kellogg had been appointed as interim replacement for the post, BBC reported.

In his letter of resignation, Flynn said he had “inadvertently briefed the vice-president-elect and others with incomplete information regarding my phone calls with the Russian ambassador”.

“I have sincerely apologized to the President and the Vice President, and they have accepted my apology,” Flynn wrote in his resignation letter, which was provided by the White House.

Flynn was known to have spoken with Russian ambassador Sergei Kislyak several times by phone in December. Flynn denied that he and  Kislyak had discussed U.S. sanctions and Vice-President Mike Pence also denied the claims on his behalf. Later, Flynn told the White House that the topic of sanctions could be discussed.