There have already been 251 mass shootings in America this year

Twenty people were killed and more than two dozen injured in a shooting Saturday in a busy shopping area in the Texas border town of El Paso on Saturday. (AP)

Two mass shootings in the space of 24 hours in the US this weekend left 29 people dead and more than 50 injured.

In the Texas border city of El Paso, a gunman stormed a shopping area packed with thousands of people on Saturday morning - killing 20 and wounding more than 24 others.

Hours later in Dayton, Ohio, a man wearing body armour and carrying extra magazines opened fire in a popular nightlife area, killing nine and injuring at least 26 people.

According to an anti-violence campaign group in the US, the shootings mean the US has now had 251 mass shootings this year alone.

The Gun Violence Archive defines a mass shooting as when four or more victims are shot or killed - not including the shooter.

Nine were killed and 26 others were injured in the second mass shooting in the U.S. in less than 24 hours. (AP)
The attack in El Paso on Saturday ranked among the deadliest mass shootings in US history. (PA)

Mark Bryant of the Gun Violence Archive has warned that the number of deadly mass shootings is 'trending higher'.

“As far as mass shooting's concerned, we're trending higher,” Bryant said in the wake of yesterday’s deadly incidents.

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Bryant said that the guns made available to “hobbyists” were extremely powerful and capable of shooting hundreds of rounds in a short space of time.

“[The] AR-15 is a gun that a lot of hobbyists use and they build up like you build up other hobbies,” he added.

Police cordoning off the crime scene after the rampage in Dayton, Ohio in the early hours of Sunday morning. (AP)

“And one of the things that you do is as you build larger magazines into the system.

“When you use them for nefarious purpose, they dump a lot of lead into a room very, very quickly.

“A hundred-round magazine literally will pull - will shoot as fast as you can pull your finger. You pull your finger a hundred times, that's maybe 10 seconds.”

In Dayton, the bloodshed was likely limited by the swift police response. Officers patrolling the area took just 30 seconds to stop the shooting.

Had police not responded so quickly, “hundreds of people in the Oregon District could be dead today,” the town’s mayor said afterwards.

In El Paso the gunman went on a rampage through a crowded Walmart store before eventually surrendering to police. (AP)
People comfort each other during a vigil for victims of Saturday's mass shooting at the shopping complex in El Paso. (AP)