A police officer stands near the suspects' vehicle after a shooting outside the Muhammad Art Exhibit and Contest sponsored by the American Freedom Defense Initiative in Garland, Texas May 3, 2015.Reuters

The Islamic State has reportedly claimed responsibility for the attack by two gunmen at a "Draw the Prophet" contest in Garland, Texas. 

The terror group made the claim through its official radio station, according to AFP. 

It was earlier suspected that the attack was Isis-inspired and carried out by men who had pledged support to Isis. But, the jihadi group has now hailed the two "soldiers of the caliphate", indicating that it was their attack. 

"Two of the soldiers of the caliphate executed an attack on an art exhibit in Garland, Texas, and this exhibit was portraying negative pictures of the Prophet Mohammed," the jihadi group reportedly said on radio. 

"We tell America that what is coming will be even bigger and more bitter, and that you will see the soldiers of ISIS do terrible things," Isis said. 

The two gunmen were shot down outside the Muhammad Art Exhibit event at the Curtis Culwell Center in Garland, Texas, where the American Freedom Defense Initiative (AFDI) had organised a contest to draw cartoons of Prophet Muhammad on Sunday. 

One of the gunmen, Elton Simpson, had allegedly pledged support to Isis. He had even posted a tweet about the attack, pledging allegiance to "Amirul Mu'mineen" - a reference to Isis leader Abu Bakr al-Baghdadi.

He had announced his martyrdom, saying, "May Allah accept us as the mujahideen," through a Twitter account named 'Shariah is Light', which bore a photo of militant Anwar Awlaki, who had been killed in a UN drone strike in Yemen in 2011.

Other Isis fighters had tweeted praises for the gunmen. 

A British Isis fighter tweeted, "2 of our brothers just opened fire at the Prophet Muhammad (s.a.w.) art exhibition in texas" and "They Thought They Was Safe In Texas From The Soldiers of The Islamic State."