The revelation cast a fresh cloud over President Donald Trump's administration, which has repeatedly denied any suspected ties between members of his election team and Russia -- which US intelligence says interfered in the 2016 campaign against Hillary Clinton.
The White House quickly labeled the report an attack by partisan Democrats, confirming the meetings but arguing Sessions did nothing wrong.
In a statement, the Trump administration's top law enforcement official, said: "I never met with any Russian officials to discuss issues of the campaign. I have no idea what this allegation is about. It is false."
"Given AG Sessions's false statements about contacts with Russian officials, we need a special counsel to investigate Trump associates' ties to Russia," said Democratic Senator Ron Wyden, a member of the Senate Intelligence Committee.
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The Washington Post reported yesterday that Sessions -- formerly a senator who advised Trump's campaign on foreign policy and other issues -- met Ambassador Sergey Kislyak in July and September, just as accusations of Russian interference in the election were mounting.
"I did not have communications with the Russians," he said under oath.
Nancy Pelosi, the top Democrat in the House of Representatives, called for Sessions to step down.
"After lying under oath to Congress about his own communications with the Russian, the attorney general must resign," she said.
Democrat Elijah Cummings of the House Oversight Committee echoed that call.
"When senator Sessions testified under oath that 'I did not have communications with the Russians,' his statement was demonstrably false, yet he let it stand for weeks," Cummings said.
A White House official dubbed the latest report an "attack."
"This is the latest attack against the Trump administration by partisan Democrats," the official said.
"Sessions met with the ambassador in an official capacity as a member of the Senate Armed Services Committee, which is entirely consistent with his testimony.