DONALD Trump has used the tragic death of missing US university student Mollie Tibbetts to illustrate America’s ‘disgraceful’ immigration laws.

The US-president slammed suspect Cristhian Bahena Rivera, 24, calling him an “illegal alien” in front of a pro-Trump rally in Virginia.

Rivera is an illegal immigrant and is being held under America’s immigration laws, according to reports.

He has been charged with first-degree murder a day after Ms Tibbetts’ body was found. If convicted, the crime carries a mandatory sentence of life in prison.

“You heard about today with the illegal alien coming in, very sadly, from Mexico and you saw what happened to that incredible, beautiful young woman,” Mr Trump said.

“Should’ve never happened. Illegally in our country. We’ve had a huge impact, but the laws are so bad. The immigration laws are such a disgrace, we’re getting them changed, but we have to get more Republicans. We have to get ‘em.”

Surveillance video was used to track down Rivera, whose car was in footage that showed Tibbetts jogging in a rural area near her hometown of Brooklyn, Iowa.

Her body was found in a field, covered with corn stalks.

During questioning, Rivera admitted making contact with Tibbetts, first by pursuing her in his car and then getting out and running beside her.

Rivera told investigators he became angry when Tibbetts showed a cell phone and threatened to call police. He said he panicked and then “blocked” his memory.

Rivera claimed he did not recall what happened but found an earpiece from headphones in his lap and realised he’d put Tibbetts’ in his trunk.

He opened the trunk and noticed blood on the side of her head. The affidavit said he carried Tibbetts’ body to a cornfield and covered her with corn stalks. When he was questioned by authorities, he led investigators to the site.

Rivera’s arrest came after Tibbetts’ body was found, bringing an end to an intensive search that lasted more than a month.

Tibbetts, who vanished in July was studying psychology at the University of Iowa, was reported missing after she failed to respond to messages from her boyfriend, Dalton Jack.

Tibbetts, who reportedly lived with her boyfriend in his older brother Blake’s home, was last seen jogging around Brooklyn, Iowa around 7.30pm on July 18.

Dalton Jack told ABC News that he received a Snapchat photo from her later that night, although it is uncertain when the photo was sent. Her family reported her missing when she did not show up for work the next day.

Last week, the FBI stated that Tibbetts had been taken by someone she knew, adding that the person was “hiding in plain sight” and had possibly even attended vigils held in the student’s honour, but no arrests were made.

The only person who has allegedly come under close scrutiny from the police is local pig farmer, Wayne Cheney.

Mr Cheney, who had reportedly plead guilty in two previous stalking cases, was reportedly questioned on multiple occasions by police and had his farm searched after police found a red T-shirt that was similar to one owned by Tibbetts near his property.

Police, however, never uncovered whether the item of clothing belonged to the missing student, and the farm was located more than 160km from where Tibbetts disappeared.

Tibbetts’ family pleaded for her safe return and had remained hopeful the 20-year-old would be found alive. Her father, Rob Tibbetts, returned home to San Francisco after spending weeks looking for his daughter.

“The bottom line is somebody knows something,” Rob Tibbetts previously told Fox News, adding Brooklyn is a small city and “you can’t do anything there without someone seeing it”.

Investigators said they followed “hundreds” of leads during the search.

“It’s totally speculation on my part, but I think Mollie is with someone that she knows, that is in over their head,” Mr Tibbetts told Fox News. “That there was some kind of misunderstanding about the nature of their relationship and at this point they don’t know how to get out from under this.”

Both Jack brothers were ruled out as possible suspects early on in the police investigation.

Tibbetts’ mother Laura Calderwood described the disappearance of her daughter as “excruciating”.

“[There are] no words to describe how you feel when you don’t know where or how your child is,” she told ABC News in the US.

The uni student’s story was widely shared on social media, with celebrities such as actor Brandon Routh and American Idol’s Maddie Poppe publicising her plight.

“She really does not have a single enemy — everybody loves Mollie,” a friend Alyssa King reportedly told People magazine, saying Tibbetts was “always trying to make people laugh”.

According to People magazine, Tibbetts planned to attend the wedding of her boyfriend’s brother in early August, about two weeks after she went missing.