(AP) BEIRUT — A U.S.-backed Syrian opposition force said Sunday it has captured a northwestern neighborhood of the Islamic State group’s de-facto capital of Raqqa the second district to fall in their hands in days after the group launched a wide offensive to gain control of the extremists’ de facto capital.

The Kurdish-led Syrian Democratic Forces said its fighters captured the neighborhood of Romaniah after two days of fighting that left 12 IS gunmen dead, including a commander known as Abu Khattab al-Tunsi.

The Britain-based Syrian Observatory for Human Rights said SDF fighters now control Romaniah and the eastern neighborhood of Mashlab. The fighters have also entered Raqqa’s western neighborhood of Sabahiya and the industrial district in the east.

Raqqa was among the first cities captured by IS, in January 2014, and has been the home of some of the group’s most prominent leaders. The battle for the city is expected to be extended and bloody, and could mark a major turning point in the war against the extremists.

IS has been fortifying its positions in Raqqa for months, setting up barriers and hanging sheets of cloth over main streets to provide cover from warplanes. A belt of land mines and militant checkpoints circle the city.

 SDF fighters began their offensive on the city of Raqqa on June 6 under the cover of airstrikes by the U.S.-led coalition.

The IS-linked Aamaq news agency said the city was subjected to intense airstrikes and shelling by the SDF and the U.S.-led coalition releasing a video that showed wide destruction in one of the neighborhoods. The video also showed severely wounded men and children being rushed to hospitals.

In southern Syria, Jordan said its border guards have killed five suspected infiltrators approaching the kingdom’s border from Syria in a pickup truck and two motorcycles.

The military said in a statement that the incident took place near the spot where Jordan, Syria and Iraq meet.

Jordan has been on alert for possible infiltrations by IS extremists who seized territories in Syria and Iraq in 2014. In recent months, Jordan expressed concern that U.S.-backed offensives against IS will push some of the militants closer to the kingdom’s border.

The army said nine vehicles approached Jordan from Syria in the past three days, and border guards opened fire to hold them back. The army says that in the latest incident, troops fired on a pickup truck and two motorcycles, killing five.