Image copyright Reuters Image caption Mr Obama said journalists need to ask Donald Trump harder questions

US President Barack Obama has said the media is partly to blame for the rise of Republican Donald Trump as a political force.

Speaking at an event for political reporters, Mr Obama said it was not enough to give "someone a microphone".

Mr Trump, a hotel tycoon who has made waves with a series of controversial remarks, is winning the race to be his party's presidential nominee.

He and the other two Republicans in contention will appear on TV later.

CNN is hosting a town hall event on Tuesday evening ahead of a crucial primary in Wisconsin next week.

Giving a keynote address at a journalists' award dinner, Mr Obama did not mention Mr Trump by name but his target was clear.

When he travels, the president said, people always ask him what is happening in American politics, because it is a place where you "can't afford completely crazy politics".

Politicians, journalists and citizens are all responsible for the divisive and bitter political atmosphere, he said, but reporters should be digging deeper on the 2016 presidential candidates.

Image copyright Reuters Image caption Mr Cruz told Mr Trump to leave his wife, Heidi, the 'hell alone'

In a reference to Mr Trump's domination of the news cycle, the president said the job of a political reporter was "more than just handing someone a microphone".

Billions of dollars in free media should come with serious accountability, especially when politicians issue unworkable plans or make promises they cannot keep, he said.

Mr Trump has had a rough couple of days in the state that will next make its choice for Republican and Democratic presidential candidates, Wisconsin.

The primary is on 5 April, with him and Texas Senator Ted Cruz neck-and-neck in the state's polls.

First he faced a hostile conservative talk-radio host, Charlie Sykes, who grilled him on his donations to Democrats and his insults to women, most recently Mr Cruz's wife.

Hear the interview in full on WTMJ

"Wouldn't it be a good way to start off your Wisconsin campaign by saying that wives should be off-limits and that you apologise for mocking her looks?" Mr Sykes asked Mr Trump during the interview.

Mr Sykes also wrongfooted Mr Trump on air by revealing he was part of the #NeverTrump movement.

Conservative websites The Federalist and RedState said Mr Trump "fell apart live on-air when asked tough questions".

Wisconsin Governor Scott Walker said on Tuesday he was backing Mr Cruz because he was the candidate most likely to win the election in November.

In the Democratic race, Hillary Clinton will try to stem the momentum of a resurgent Bernie Sanders, who is on a roll after a string of wins.