A Diggers Rest man has admitted to murdering his 29-year-old girlfriend by bashing her to death.

Shane Robertson faced Melbourne Magistrates Court on Tuesday and pleaded guilty to murdering former hairdresser Katherine Haley on March 9, 2017.

The court heard that Robertson killed the mother-of-two by striking her five times to the head with a dumb-bell bar on the night they broke up at their Diggers Rest home.

Ms Haley’s body was identified by her dental records.

A large group of Ms Haley’s family were present at Tuesday’s hearing, including her father, sister, aunt and cousin.

Several women cried during the proceeding.

Emergency services were called to the home in Fairfield Crescent shortly after 11pm that night.

Ms Haley’s body was found fully clothed and she had suffered extensive head trauma.

Robertson was charged with murder the next day.

The pair had previously been described as a “very happy and a very lovely couple”.

Police said Robertson became jealous after Ms Healy started a waitressing job after the birth of her second child. He didn’t like her working at a pub with men and believed she was cheating on him.

Robertson also made Ms Haley give him her phone so he could look at her social media accounts, forced her to delete those accounts, and to stop speaking to male co-workers, police said.

In the weeks before the murder, Ms Haley told friends Robertson had become possessive and she was thinking of leaving him.

Early on the morning of the murder, Robertson messaged Ms Haley: “Good night babe, had a good night with not only my best friend but my life partner. Here’s to our new beginning at life.”

He messaged and called her repeatedly throughout the day before the pair went out for dinner and went home.

However, an argument broke out between the couple over Ms Haley using her mobile phone, court documents show, and she told Robertson that she didn’t love him any more.

Following the murder, Robertson called his mother and said: “I kill her mum. I kill her. I didn’t mean it” and later: “I’ve done it. I’ve bashed her brains in. There is brains everywhere”, the court heard.

The court was previously told Robertson was at risk of self-harm and was having suicidal thoughts in custody.

He was remanded to appear at the Supreme Court on Friday for a directions hearing.

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Amber Wilson, The Age