Several relatives of Mollie Tibbetts have called for her death not to be politicised after Donald Trump blamed the Iowa college student's murder on "weak" immigration laws.

Mr Trump said the case showed the need for the United States to build a wall on the Mexico border.

The body of Miss Tibbetts, 20, was found in a corn field in Iowa a month after she vanished while out jogging.

Christhian Rivera, 24, has been arrested and charged with murder, and appeared in a rural court house in Iowa on Wednesday.

Police have said Rivera is a Mexican who was in the country illegally.

His employer, an Iowa dairy farm, said he had looked after cows there, using a fake identity card to pass employment checks and collecting his pay under a false name.