Four men who allegedly attacked a gay couple at Miami Pride have now been charged with a hate crime, potentially doubling their prison sentences if convicted.

During last month’s Miami Beach Pride, two gay men were attacked and beaten to the ground, in the attack by four men in Miami Beach.

Rene Chalarca and Dmitry Logunov were knocked to the ground and then repeatedly punched and kicked in the attack on April 8, which the pair claimed have said was prompted because they were holding hands.

A man who attempted to intervene also suffered a laceration to the back of his head.

Four men handed themselves into the police over the attack, after authorities released CCTV as part of a public appeal for help.

The suspects were originally charged with aggravated battery after the attack, which carries a maximum prison sentence of 15 years.

However, in the state of Florida, the enhanced hate crime charges mean that the alleged perpetrators could face as much as 30 years in prison.

On Thursday, the Florida state attorney’s office made the decision to classify the attack as a hate crime.

State Attorney Katherine Fernández Rundle announced the news on Twitter.

She wrote: “The four defendants arrested for assaulting two gay individuals during the Gay Pride Parade on South Beach last month were charged today with hate-crime related felony offences.

“I commend the investigative work of the Miami Beach Police Department and my Hate Crimes Unit prosecutors in this case.”

Related: Gus Kenworthy crowd surfed at Miami Beach Pride and it was truly iconic

The four suspects – Juan C. Lopez, Adonis Diaz, Pablo Reinaldo Romo, all 21, and Luis M. Alonso, 20 – were arrested and charged after the self-surrender.

The couple were treated by paramedics at the scene for cuts and bruises on their faces, while the man who attempted to stop the attack, Helmut Muller Estrada, was taken to Mount Sinai Medical Center where his head wound required four stitches.

Mr Chalarca said the pair are sure they were targeted because they are gay and were holding hands.

Speaking to local outlets WTVJ and WSVN, he said: “The way we were dressed and everything. We were together. For me, it was like, yes, it was a hate crime.”

He added: “It was my first time going to these events, and for me it’s overwhelming.

“It was like, something in my stomach went down and then up, and I was like, I don’t know how to react.”

The four men have pleaded not guilty.