A radio state associated with Islamic State (Isis) has called the gunman responsible for the Orlando shooting "one of the soldiers of the caliphate in America".

Omar Mateen, who killed at least 50 people and injured 53 more when he opened fire at gay nightclub Pulse, was mentioned by Al-Bayan Radio, which said he had targeted Christians and homosexuals.

Mateen, whose attack is the worst shooting in recent US history, reportedly pledged his allegiance to Isis in a phone call to the emergency services during the massacre.

Isis news agency Amaq later claimed responsibility for the attack, stating the shooting had been carried out "by an Islamic State fighter", although it is not clear whether Isis had any prior knowledge of the hate crime.

The attacker fired rounds from an AR-15 assault rifle inside the club, being drawn outside by fire from a police officer on duty at Pulse when the shooting began, around 2am on 12 June.

However, Mateen re-entered the club to continue his massacre, while revellers who had been enjoying a night of dancing attempted to flee the building, many barricading themselves into the bathrooms in a bid to hide from the shooter.

The gunman's father said his son had become incensed after seeing two men kissing in Miami several months earlier.

Messages of support for the victims have come in from world leaders and LGBTQ charities around the globe, with an evening of vigils planned in different cities to remember those who lost their lives in the shooting.

Omar Mateen
Omar Mateen, who carried out the mass shooting at the Pulse nightclub in Orlando Reuters