Two gunmen were shot dead following a shootout at a 'Muhammad Art Exhibit and Cartoon Contest' at Curtis Culwell Centre in Texas city of Garland.
The City of Garland administration, in a statement on its Facebook page, said: 'As today's Muhammad Art Exhibit event at the Curtis Culwell Centre was coming to an end, two males drove up to the front of the building in a car. Both males were armed and began shooting at a Garland ISD (Independent School District) security officer. Garland Police officers engaged the gunmen, who were both shot and killed."
It added that police suspected the gunmen's vehicle could contain an "incendiary device" and a bomb squad was at the scene.
About 200 people were inside the conference centre at the time and were moved to the back of the building before being evacuated using school buses, police said.
The event with $10,000 prize for the best cartoon of the Prophet Muhammad, was being held by the American Freedom Defence Initiative, which has reportedly said it was exercising the freedom of expression.
The event was aimed at symbolising the significance of free speech "in response to the outcries and violence over drawings of Muhammad", Pamela Genner said as per a news agency.
Pamla Genner, who runs the American Freedom Defence Initiative, took to Twitter to report about the incident saying, "This is a war. This is war on free speech. What are we going to do? Are we going to surrender to these monsters?".
The shooting comes four months after gunmen killed 12, including 8 journalists at the office of French satirical magazine Charlie Hebdo which had published Prophet's cartoons.
The attack on Charlie Hebdo magazine in Paris had sparked worldwide concern, triggering a debate over the free speech.
Any form of drawing or art depicting Prophet Muhammad is considered blasphemous in Islam.
In January, 12 people were killed by gunmen in an attack against the Paris office of the satirical newspaper Charlie Hebdo, which had lampooned Islam and other religions and used depictions of Muhammad.
