Washington (AFP) - President Barack Obama said Friday he had confronted Vladimir Putin in person over allegations of Russian hacking when they met ahead of the US election, telling him to "cut it out."

US President Barack Obama holds a year-end press conference in the Brady Press Briefing Room of the White House in Washington, DC, December 16, 2016 © AFP Saul Loeb Washington (AFP) - President Barack Obama said Friday he had confronted Vladimir Putin in person over allegations of Russian hacking when they met ahead of the US election, telling him to "cut it out."

After being alerted over the summer to Russian cyber attacks on the Democratic Party, Obama told a year-end news conference his chief concern was to ensure the hacking did not escalate and hamper the vote counting last month.

"In early September when I saw President Putin in China, I felt that the most effective way to ensure that that didn't happen was to talk to him directly and tell him to cut it out and there were going to be serious consequences if he didn't," Obama said.

"And in fact we did not see further tampering of the election process," he added.

Just five weeks before he leaves the White House, the outgoing president has vowed to retaliate against Moscow over the cyber-meddling, which US intelligence says was designed to help Republican Donald Trump defeat Democrat Hillary Clinton, a Putin critic.

"Our goal continues to be to send a clear message to Russia or others not to do this to us because we can do stuff to you," warned the US president.

Obama said there also was "some evidence" of China curbing cyber espionage in response to US warnings.

"I had to have the same conversation with President Xi (Jinping) and what we've seen is some evidence that they have reduced but not completely eliminated these activities," the US leader said.

Obama's traditional year-end press conference -- held as tensions soar with Russia -- was expected to be closely watched by his elected successor Trump, who has pledged to foster closer ties with the Kremlin.

While Obama has not directly named Putin over the election hacking, one of his top advisors, Ben Rhodes, said Thursday: "I don't think things happen in the Russian government of this consequence without Vladimir Putin knowing about it."

Meanwhile US officials said a Chinese warship had seized a US underwater drone in the South China Sea, triggering a formal diplomatic protest.

The Global Times cited a Chinese military source as saying Beijing believed the incident involving the U.S. drone would be resolved "smoothly."