President-elect Donald Trump on Wednesday flatly denied “phoney” explosive allegations about ties with Russia and lurid behaviour on a trip to Moscow that have tainted his election victory and threatened to engulf his presidency.

Just over a week before Trump takes office, the United States has been rocked by unsubstantiated claims that his aides colluded with the Kremlin to win the election — and that Russia has compromising sexual material on Trump.

“I think it's a disgrace that information would be let out,” Trump said, training fire on media outlets that published the allegations and the intelligence agencies who he suggested may have leaked it.

“It's all fake news. It's phoney stuff. It didn't happen,” he said in his first press conference in nearly six months.

“It was a group of opponents that got together, sick people, and they put that crap together.”

It “was released by maybe the intelligence agencies, who knows, but maybe the intelligence agencies, which would be a tremendous blot on their record,” Trump said, later saying it was “disgraceful.”

Turned over 'complete' control of business to sons

Donald Trump said he had formally handed “complete and total” control of his business empire to his adult sons, Don Jr and Eric, in a bid to avoid conflicts of interest once he enters the White House.

“My two sons, who are right here, Don and Eric, are going to be running the company. They are going to be running it in a very professional manner. They're not going to discuss it with me,” the president-elect told a news conference.

Trump said he had signed documents “turning over complete and total control to my sons.”

Mexico will reimburse US for cost of border wall

Donald Trump vowed to forge ahead with plans for a wall on the southern US border after taking office, and said Mexico would reimburse the United States for the cost.

“I could wait about a year and a half until we finish our negotiations with Mexico, which we'll start immediately after we get to office, but I don't want to wait,” Trump told the news conference.

“We're going to start building,” he said, adding: “Mexico in some form — and there are many different forms — will reimburse us and they will reimburse us for the cost of the wall.”

“That will happen. Whether it's a tax or whether it's a payment.“

Trump warns US firms moving jobs offshore, singling out pharma

In his press conference, Trump attacked US companies who ship jobs offshore, singling out the pharmaceutical industry for high drug prices and for manufacturing overseas.

Trump said US companies relocating production offshore are “getting away with murder” and warned their products will be hit with hefty taxes if imported into the United States.

“There will be a major border tax on these companies that are leaving and getting away with murder,” he told his first press conference.

“The word is now out that when you want to move your plant to Mexico or some other place, and you want to fire all of your workers from Michigan and Ohio and all these places that I won, for good reason, it's not going to happen that way anymore,” he said.

“You are going to pay a very large border tax.”

Shares of drugmakers plummeted as Trump singled out the massive industry, warning he would seek to cut prices by restructuring procedures for bidding on drugs.

“Pharma. Pharma has a lot of lobbies, a lot of lobbyists, a lot of power,” he said, making the industry the latest target of his frequent attacks on business since the November election which have included the auto and aerospace industries.

“Our drug industry has been disastrous. They're leaving left and right. They supply our drugs but they don't make them here, to a large extent,” Trump said.

To address high prices, “the other thing we have to do is create new bidding procedures for the drug industry,” he said.

The United States is “the largest buyer of drugs in the world” but does not bid properly, he said.

With the changes to bidding procedures, which he did not specify, “We're going to save billions of dollars.”

Trump claimed credit for recent announcements by auto makers Ford and Fiat-Chrysler of plans to boost investments in the United States, and in the case for Ford, cancelling a $1.6 billion plant in Mexico.