Media playback is unsupported on your device Media caption Democrats stall committee votes on cabinet picks

US Senate Democrats are boycotting confirmation votes for two of President Donald Trump's key cabinet nominees, forcing the votes to be postponed.

Senate committees had been expected to approve several candidates, in the second week of Mr Trump's presidency.

Democrats said they wanted more information about the financial activities of health nominee Tom Price and treasury pick Stephen Mnuchin.

Mr Trump had earlier said the Democrats were obstructing the political process.

A vote on attorney general nominee Jeff Sessions was also postponed.

On Monday the acting attorney general was sacked for questioning the legality of Mr Trump's immigration directive.

It imposes a temporary travel ban on seven mainly-Muslim countries.

Acting Attorney General Sally Yates had been appointed by President Barack Obama.

'Acting like idiots'

Democratic Senators from the Finance Committee told reporters outside the hearing for health and treasury nominees that they were seeking more information about Tom Price's trading in health company stock.

Media playback is unsupported on your device Media caption Muslim students on Trump ban: 'I don't belong here'

The Georgia Congressman has been nominated for the post of health and human services secretary in the new administration.

The senators said they were also concerned by reports of financier Stephen Mnuchin's behaviour involving foreclosures at his former bank OneWest.

Democrats get tough, by Anthony Zurcher, BBC News

Image copyright AFP Image caption Democrats explained to the press why they were boycotting the Finance Committee votes

The unexpected walkout by Democrats during scheduled votes to advance two of Donald Trump's more controversial cabinet nominees may be the first shots that lead to total partisan warfare on Capitol Hill.

Democratic senators had been subjected to growing criticism from the grass-roots Left for being too accommodating to Mr Trump and his nominees. On Sunday, for instance, more than 200 protesters descended on Senator Diane Feinstein's California house after she voted to confirm four earlier administration nominees.

Now, it seems, Democrats could be heeding the anger of their base and taking a more combative posture toward Republicans in general and Mr Trump in particular. These politicians likely saw Acting Attorney General Sally Yates become a liberal hero for defying the president on Monday night and are recognising that their party's anger is a force that could propel their careers or tear them apart.

This does not bode well for Mr Trump's Supreme Court nominee, who will be announced on Tuesday night. While Senate Democrats have had to rely on byzantine parliamentary manoeuvres to delay Mr Trump's cabinet picks, they have a powerful weapon - the filibuster - at their disposal to indefinitely block the president's high court selection.

But Senator Orrin Hatch, the Republican committee chair, described the Democrats' behaviour as "posturing and acting like idiots", AP reported.

A battle also raged in the Senate Judiciary Committee, where Mr Sessions came under heavy criticism.

An early Trump backer, Senator Sessions has faced racism allegations which overshadowed his confirmation hearings.

Committee chairman Senator Chuck Grassley began Tuesday's meeting by saying that neither Mr Sessions nor any of his current staff, "had a role in formulating or drafting the executive orders" - including the controversial travel ban.

Media playback is unsupported on your device Media caption Jeff Sessions said caricature of him as a "Southern racist was painful"

Several Democratic Senators spoke in the committee meeting to say that they intended to vote against the 69-year-old Alabama senator.

Sen Diane Feinstein criticised his role in Mr Trump's election campaign and his closeness to the new president during it.

"It is very difficult to reconcile for me the independence and objectivity necessary for the position of attorney general with the partisanship this nominee has demonstrated," she said.

The Democrats' lengthy speeches extended the hearing into the afternoon, eventually forcing Sen Grassley to postpone the vote until Wednesday.

If Mr Sessions' nomination is approved by the judiciary committee, the full Senate - where Republicans hold a 52-48 majority - is expected to vote on it by the end of the week.

Early on Tuesday, Mr Trump expressed his frustration at the wait in confirming Mr Sessions' appointment.

He tweeted: "When will the Democrats give us our Attorney General and rest of Cabinet! They should be ashamed of themselves! No wonder D.C. doesn't work!"

"The Democrats are delaying my cabinet picks for purely political reasons. They have nothing going but to obstruct," he added.

Media playback is unsupported on your device Media caption In 2015, Jeff Sessions asked Sally Yates if the attorney general should ever say no to the president

The Alabama senator faced two days of tough questioning during his confirmation hearings this month.

One of the most conservative members of the Senate, Mr Sessions was denied a federal judgeship in 1986 after the judiciary committee heard testimony about his remarks on race.

Media playback is unsupported on your device Media caption The Supreme Court has been without a full bench for almost a full year.

Also on Tuesday:

Mr Trump's choice to fill the long-vacant seat on the Supreme Court is due to be announced

The Senate Energy Committee approves Ryan Zinke to head the Interior Department and Rick Perry to head the Energy Department

The Education Committee approves Betsy DeVos as education secretary

The full Senate confirmed Elaine Chao as transportation secretary; she has now been sworn in

The attorney general is America's top prosecutor, leads the justice department and acts as the main adviser to the president on legal issues.

Ms Yates was sacked by President Trump, who accused her of "betraying" the justice department and being "weak on borders".

She had said in a letter that she was "not convinced" that the president's order on immigration was lawful.

Mr Trump replaced her with Dana Boente, a federal prosecutor for the Eastern District of Virginia.

The immigration order, signed by the president on Friday, temporarily banned nationals from Iraq, Syria, Iran, Libya, Somalia, Sudan and Yemen from entering the US. It sparked protests in the US and abroad.

The White House has consistently defended Mr Trump's executive order despite the controversy, with press secretary Sean Spicer saying diplomats should "get with the programme".