ISTANBUL, Turkey — Four refugee children were killed when Islamic State militants shelled a Turkish city near the Syrian border this week. The extremist group has stepped up its attacks on the city of Kilis, which hosts a large number of Syrian refugees.

Islamic State militants fired five rockets at the city Monday, local authorities confirmed.

Three children were killed during the attack; a fourth on Tuesday succumbed to injuries. The rockets also killed a Syrian shepherd and wiped out much of his flock.

The four children had taken shelter in a building run by the Yavuz Sultan Selim Foundation, a local charity that provides support to the dependents of refugees who have been killed, Turkey’s state-run Anadolu Agency reported.

Kilis lies six miles from the nearest border crossing with Syria. About 110,000 Syrian refugees have taken shelter there. It is the only Turkish city in which the Syrian population exceeds that of local Turks.

The Turkish government hopes to see Kilis, which had a prewar population of 85,000, nominated for the Nobel Peace Prize in recognition of its efforts in providing a haven for Syrians fleeing the conflict in their homeland.

The Turkish military retaliated against the Islamic State attack, targeting positions in the farmlands of northern Syria. “Our army officials are locating their coordinates and destroying them with artillery fire,” Kilis Gov. Suleyman Tapsiz said, according to Reuters.

Islamic State has barraged the city with rockets several times this month, injuring about two dozen people and killing six. Three people were injured Tuesday as the extremists again targeted the city, according to the Anadolu Agency.

Angry residents took to the streets last week, gathering in front of the governor’s office to demand that the authorities provide better protection.

The attacks may be retribution for Turkey’s increasing role in the U.S.-led coalition’s fight against Islamic State and its support for a loose coalition of Syrian rebel factions fighting under the banner of the Free Syrian Army.

Those factions, buttressed by Turkmen militias and the hard-line group Ahrar al Sham, recently made dramatic advances against Islamic State in the countryside of northern Syria and took the Islamic State-controlled town of Rai, part of a broader push toward the group’s stronghold in the city of Jarabulus.

Turkey supported the offensive with artillery bombardments.

Islamic State launched a potent counteroffensive last week, driving back the rebel groups and displacing tens of thousands of people. They also took control of at least two camps for internally displaced people.

The aid agency Doctors Without Borders alleged that as many as 100,000 people have been displaced during the latest bout of fighting and have sought shelter in areas along the border. It called on the European Union to assure the safety of the displaced.

“Yet again we see tens of thousands of people forced to flee but with almost nowhere safe to go – trapped in this bloody, brutal conflict,” Muskilda Zancada, the group’s head of mission for Syria, said in a statement Monday. “We are extremely worried about the protection of the population if the front lines keep approaching.”

Turkey, struggling with what it says are 2.7 million refugees on its soil and under pressure to stem the flow of refugees into the European Union, has closed its borders to the displaced, repeatedly firing live ammunition at Syrians attempting to enter the country, and has granted entrance to only the most seriously injured.