BARCELONA, Spain — A van veered onto a sidewalk and sped down a busy pedestrian zone Thursday in Barcelona’s picturesque Las Ramblas district, swerving from side to side as it mowed down tourists and residents and turned the popular European vacation spot into a bloody killing zone. Thirteen people were killed and 100 were injured, 15 of them seriously, in what authorities called a terror attack.

Victims were left sprawled in the street, spattered with blood or crippled by broken limbs. Others fled in panic, screaming or carrying young children in their arms.

“It was clearly a terror attack, intended to kill as many people as possible,” Josep Lluis Trapero, senior police official, told a news conference late Thursday.

The Islamic State group claimed responsibility, saying in a statement on its Aamaq news agency that the attack was carried out by “soldiers of the Islamic State” in response to the extremist group’s calls for followers to target countries participating in the coalition trying to drive it from Syria and Iraq.

After the afternoon attack, Las Ramblas went into lockdown. Swarms of police brandishing hand guns and automatic weapons launched a manhunt in the downtown district, ordering stores and cafes and public transport to shut down.