Republican presidential candidate Donald Trump's hardline immigration plan has been savaged by his rivals during a televised debate.

Mr Trump's was booed at one point, shortly after calling for all illegal migrants to be deported.

Candidates John Kasich and Jeb Bush were very critical, saying penalties and tighter border security was needed.

The top eight Republican presidential contenders are squaring off in Milwaukee for the fourth time.

Mr Trump reiterated his calls for a wall to be built at the US-Mexico border and for migrants currently living illegally in the US to be deported.

Mr Kasich, the governor of Ohio, shot back imploring his opponent to "think about the children".

"It's a silly argument," he said of Mr Trump's plan. "It's not an adult argument."

Mr Bush, the former Florida governor under pressure to revive a flagging campaign, also condemned the plan, saying it would tear families apart.