BAGHDAD -- Iraqi riot police opened fire Tuesday amid clashes with anti-government protesters on a central Baghdad highway, killing one person and wounding over a dozen others, officials said. They were the latest casualties since violence erupted again last week between demonstrators and security forces.

Clashes on the key Mohammed al-Qassim highway broke out when riot police moved in to disperse a crowd of mostly young men who had gathered there. The protesters burned tires, halting traffic along the key artery and some protesters hurled Molotov cocktails, or fire bombs, at the riot police.

Police fired live rounds and tear gas canisters at the crowd. At least 14 protesters were wounded, their injuries ranging from severe to moderate. One protester died after being struck by a tear gas canister to the head, according to police and medical officials and activists.

As the violence escalated, police pulled back, allowing demonstrators to take over the thoroughfare, witnesses said, speaking on condition of anonymity, fearing reprisals.

The Mohammed al-Qassim highway connects areas in Baghdad's Rusafa, a district to the east of the Tigris River. Protesters have already blocked three central bridges - the Sinak, Jumhuriyah and Ahrar. Blocking the highway threatens to halt movement altogether in the central part of Baghdad.

Meanwhile, outgoing Prime Minister Adel Abdul-Mahdi condemned an overnight triple-rocket attack targeting the heavily fortified Green Zone, the seat of Iraq's government, and ordered an investigation into the incident, military spokesman Maj. Gen. Abdul Karim Khalaf said. The Katyusha rockets fell near the U.S. Embassy but caused no casualties.

The Green Zone attack was the second rocket attack to target the area in the last two weeks, amid soaring tensions between Washington and Tehran after a U.S. drone strike killed top Iranian Gen. Qassem Soleimani in Baghdad earlier this month.

A statement from Baghdad Operations Command said security forces had found the rocket launchers used in the attack in the Zafaraniya area of the capital.

According to a security official, two of the rockets had breached the outermost fence but did not strike near the embassy's heavily fortified walls. All the officials spoke on condition of anonymity under regulations.