At least four boats have sunk at a 'Trump Boat Parade' event on Lake Travis.

Several boats have sunk during the parade that aimed to show support for President Donald Trump ahead of November's election. 

Authorities say the choppy water was likely caused by the large number of vessels moving closely together on Lake Travis, near the state capital, Austin.

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Travis County Sheriff's Office spokeswoman Kristen Dark said: "We responded to multiple calls of boats in distress, several of them sank," she said. "We had an exceptional number of boats on the lake today... When they all started moving at the same time, it generated significant waves."

Images showed boats with Trump campaign flags manoeuvring near other boats with authorities say the choppy water was likely caused by the large number of vessels moving closely together. 

Multiple agencies quickly moved to assist people with were no immediate reports of injuries.

The event, called Lake Travis Trump Boat Parade, was organised on Facebook, and more than 2,600 people marked themselves as having attended it.