Puerto Rico has been struck by a magnitude-6.5 earthquake just before dawn on Tuesday (local time), the largest in a series of quakes that have struck the US territory in recent days and caused heavy damage in some areas.

Key points: Puerto Rico has recorded its largest quake over the past week, at magnitude-6.5

Puerto Rico has recorded its largest quake over the past week, at magnitude-6.5 Over 30 houses were heavily damaged by the previous magnitude-5.8 quake

Over 30 houses were heavily damaged by the previous magnitude-5.8 quake Despite the tsunami alert, Puerto Rico's Seismic Network said no risk remains

A tsunami alert was initially issued for Puerto Rico and the US Virgin Islands, but director of Puerto Rico's Seismic Network, Victor Huerfano, told local media there was no risk of a tsunami.

The US Geological Survey said the quake hit at 4:24 am just south of the island at a shallow depth of 10 kilometres.

There were no immediate report of injuries or damage but the Electric Power Authority reported an island-wide power outage.

A magnitude-5.8 quake that struck early on Monday morning collapsed five homes in the south-west coastal town of Guanica and heavily damaged dozens of others.

It also caused small landslides and power outages. The quake was followed by a string of smaller temblors.

The town of Guanica was hit particularly hard. ( AP: Carlos Giusti )

The shake also collapsed a coastal rock formation that had formed a sort of rounded window, Punta Ventana, that was a popular tourist draw in the southwest town of Guayanilla.

Residents in the south of the island have been terrified to go into their homes for fear that another quake will bring buildings down.

The flurry of quakes in Puerto Rico's southern region began the night of December 28.

Mr Huerfano said shallow quakes were occurring along three faults in Puerto Rico's southwest region: Lajas Valley, Montalva Point and the Guayanilla Canyon.

He said the quakes overall come as the North American plate and the Caribbean plate squeeze Puerto Rico.

In the southern town of Guanica, Mayor Santos Seda said five homes had collapsed during the previous quake.

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He said another 29 homes were heavily damaged and about to collapse.

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The emergency management director for the southern coastal city of Ponce, Angel Vazquez, said power outages were reported in some parts of Puerto Rico following the quake.

"This is one of the strongest quakes to date since it started shaking on December 28," he said.

"It lasted a long time."

Residents in southern coastal towns began posting pictures of partially collapsed homes and large boulders blocking roads on social media as officials urged people to remain calm.

Dr Sindia Alvarado, who lives in the southern coastal town of Penuelas, said she was petrified.

"My entire family woke up screaming," she said.

"I thought the house was going to crack in half."

Five homes were destroyed in the coastal town of Guanica. ( AP: Carlos Giusti )

At a hotel in Guanica, people panicked as they tried to flee in their cars, only to realise that large boulders were obstructing the only highway heading north to the capital San Juan, lawyer Jose Francisco Benitez said.

"There was a state of panic," he said.

The flurry of quakes in Puerto Rico's southern region began the night of December 28, with quakes ranging in magnitude from 4.7 to 5.1.

The natural stone arch of Punta Ventana is seen before it was destroyed in the earthquake. ( Edgar Gracia via AP )

Previous quakes of lesser magnitudes in recent days have cracked homes and led to goods falling off supermarket shelves.

Victor Huerfano, director of Puerto Rico's Seismic Network, said that shallow quakes were occurring along three faults in Puerto Rico's south-west region: Lajas Valley, Montalva Point and the Guayanilla Canyon.

He said the quakes come as the North American plate and the Caribbean plate squeeze Puerto Rico, and that it was unclear when they would stop or if bigger quakes would occur.

The earthquake left many homes badly damaged. ( AP: Carlos Giusti )

Puerto Rico does not have a public earthquake warning system, except for sirens that are supposed to ring in case of a tsunami.

Residents criticised the Government for what they believe is a lack of action.

One of the largest and most damaging earthquakes to hit Puerto Rico occurred in October 1918, when a magnitude-7.3 quake struck near the island's north-west coast, unleashing a tsunami and killing 116 people.

AP/Reuters