Amber Heard burst into tears and struggled to finish sentences during her testimony at a US defamation trial as she described how Johnny Depp had allegedly violated her with a bottle.

The actress said that during a violent argument with her former partner, Mr Depp had held her by the throat and smashed glass at a property in Australia in March 2015.

Mr Depp is suing the Aquaman star for libel over a 2018 article she wrote in The Washington Post which his lawyers say falsely implies he physically and sexually abused her while they were together.

The actor has denied all accusations.

Describing the alleged 2015 incident during the second day of her evidence, Ms Heard told jurors that following a struggle they had ended up on a counter top and she had felt “pressure on my pubic bone”.

“I felt this pressure, I thought he was punching me. I saw his arm. I could feel his arm and it looked like he was punching me,” she said, her voice breaking.

“I felt pain and pressure on my pubic bone.

“I don’t remember what I said, I just remember being really still…looking around the room, all the broken bottles, broken glass.”

Ms Heard’s lawyer Elaine Bredehoft asked the actress to clarify the graphic details of the alleged penetration, which she did.

“I was heartbroken (but)…the discomfort I was feeling afterwards paled in comparison with how scared and shocked I was.”

The actress said Mr Depp had also broken a phone at the property “into smithereens”, ripped her nightgown off, and screamed at her repeatedly that he would “f****** kill” her.

Jurors heard that the morning after the alleged incident Ms Heard had discovered “incoherent” messages written in navy-blue and brown paint, and food smeared on the walls of the property.

She added that pieces of raw meat wrapped in a silk gown she owned had been hidden in various locations around the property.

“It was bizarre,” she said.

She later added that she had been “destroyed” by the incident and had feared leaving to go home because Mr Depp might harm himself.

“I was worried we couldn’t come back from what had happened…that there was no way we could turn it around,” she said.

During another incident she said Mr Depp had held her into a pillow-top and she had feared she could die as she struggled to breathe.

The court was also shown several pictures of Ms Heard displaying injuries she had allegedly received during the violent altercations with Mr Depp.

Earlier, she detailed to the court other instances of “disgusting” verbal and physical abuse she had allegedly suffered at the hands of the actor.

The court heard the relationship had become a “constant battle” and that Mr Depp had taken particular issue with her professional relationship with actor James Franco, whom he “hated”.

They were also played audio clips of an incident on a plane in May 2014 in which Ms Heard alleges she was kicked in the back by the actor, who became so intoxicated he “howled like an animal”.

Ms Heard took to the witness box for the first time on Wednesday and tearfully described other incidents of alleged violence including one where Mr Depp had performed a “cavity search” on her.

On both days Mr Depp has not made eye contact with Ms Heard while she has been giving evidence.

Outside the courthouse, hundreds of fans queued to get into the building to watch the trial, some having camped overnight on the grounds – in contravention of a previous police order.

The large public interest has resulted in limited capacity for journalists also trying to get into the courtroom.

Proceedings at the Fairfax County District Court will take a break for one week, after which Ms Heard will resume giving evidence on May 16.