The attacker, driving a Humvee vehicle packed with explosives and likely stolen from defeated government troops, also wounded 60 Shi’ite militiamen, who had helped government forces retake the town just south of the capital.
Holding Jurf al-Sakhar is critical for Iraqi security forces who finally managed to drive out the Sunni insurgents after months of fighting.
It could allow Iraqi forces to prevent the Sunni insurgents from edging closer to the capital Baghdad, sever connections to their strongholds in western Anbar province, and stop them infiltrating the mainly Shi’ite Muslim south.
The group has threatened to march on Baghdad, home to special forces and thousands of Shi’ite militias expected to put up fierce resistance if the capital comes under threat.
Gains against Islamic State, an al Qaeda offshoot made up of Arab and foreign fighters, are often fragile even with the support of U.S. airstrikes on militant targets in Iraq and neighboring Syria.
As Iraqi government soldiers and militias savored their victory and were taking photographs of Islamic State corpses on Sunday, mortar rounds fired by Islamic State fighters who had fled to orchards to the west rained down on Jurf al-Sakhar.
The blast hit the militiamen, killing dozens and scattering body parts, according to a Reuters witness.
The next significant fighting near Baghdad is expected to take place just to the west in the Sunni heartland Anbar province.
The town of Amriyat al-Falluja has been surrounded by Islamic State militants on three sides for weeks. Security officials say government forces are gearing up for an operation designed to break the siege.
Gains in the Islamic State stronghold of Anbar could raise the morale of Iraqi troops after they collapsed in the face of a lighting advance by the insurgents in the north in June.
NO LETUP TO THE VIOLENCE
Islamic State kept up the pressure on security forces on Monday, attacking soldiers, policemen and Shi’ite militiamen in the town of al-Mansuriyah, northeast of Baghdad. Six members of the Iraqi security forces were killed, police said.
Kurdish peshmerga fighters also made advances over the weekend against Islamic State, which has declared a caliphate in the heart of the Middle East and is determined to redraw the map of the oil-producing region.
Much attention is focused on the planned deployment of peshmerga to the besieged Syrian border town of Kobani, where fellow Kurds have been fending off an attack by Islamic State for 40 days.
Iraqi Kurdish officials and a member of the Kurdish administration in Syria said the peshmerga had been due to head to Kobani via Turkey on Sunday but their departure had been postponed.
“Until now they have not gone,” said Sinam Mohammed, the Syrian Kurdish administration’s representative in Europe. “They were supposed to go yesterday. They (KRG) says we are ready to send them but I don’t know what happened. I think the problem is Turkey.”
Iraqi Kurdish forces will not engage in ground fighting in the Syrian town of Kobani but provide artillery support for fellow Kurds there, a Kurdish spokesman has said.
Islamic State fighters have been trying to capture Kobani for over a month, pressing on despite U.S.-led air strikes on their positions and the deaths of hundreds of their fighters.
The Kurdish region’s parliament voted last week to deploy some of its peshmerga forces, which have been fighting their own battle against Islamic State in the north.
There were heavy clashes and sporadic exchanges of mortar fire in Kobani on Monday, with several plumes of gray smoke rising over the east of the town, where fighting has been intense in recent days.
Islamic State militants tried to seize a border post just to the east of Kobani over the weekend but were repulsed by Kurdish fighters. -Reuters