Donald Trump questions White House's prolonged silence over Russia hacking

Trump's tweet comes days after Obama issued orders for an investigation into alleged hacking by Russia

US president-elect Donald Trump on Thursday questioned the White House's motive over ordering an investigation into alleged Russian hacking of the Democratic Party's servers and emails of campaign officials of his defeated presidential rival Hillary Clinton.

"If Russia, or some other entity, was hacking, why did the White House wait so long to act? Why did they only complain after Hillary lost?" Trump tweeted.

Trump's tweet comes days after the White House said President Barack Obama has issued orders for an investigation into alleged hacking by Russia or other countries into the servers of the Democratic National Committee and of emails of Clinton's presidential campaign aides.

A day earlier the White House said Trump knew before the elections that Russia was behind the hacking.

"There's ample evidence that was known long before the election and, in most cases, long before October about the Trump campaign and Russia -- everything from the Republican nominee himself calling on Russia to hack his opponent," White House Press Secretary Josh Earnest said.

"It might be an indication that he was obviously aware and concluded, based on whatever facts or sources he had available to him, that Russia was involved, and their involvement was having a negative impact on his opponent's campaign. That's why he was encouraging them to keep doing it," Earnest said.

A secret assessment by CIA has concluded that Russia intervened in the election to help Trump, the Washington Post had reported, citing officials briefed on the matter.

"You had the Republican nominee refer to the President of Russia as a strong leader. The Republican nominee chose a campaign chair that had extensive, lucrative, personal financial ties to the Kremlin," Earnest said.

In an interview last week, Trump had accused the Democratic Party of using hacking as an excuse for its defeat.

"I think, the Democrats and putting it out because they suffered one of the greatest defeats in the history of politics in the country," Trump said adding no one knows who was behind the hacking.