BEIRUT / RAQQA, Syria: U.S.-backed Syrian fighters seized a second district of Raqqa Sunday and launched a renewed assault on a base north of the city, as they pursued an offensive against Daesh (ISIS).

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

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

While it has advanced steadily against Daesh inside east and west Raqqa, the militant group’s de facto capital, it has made less progress on the northern front, where militants are using a military base and adjacent sugar factory to defend the approach into the city.

SDF fighters were battling Sunday to dislodge the militants from the Division 17 base, with backing from the U.S.-led coalition bombing Daesh, the Observatory said.

“Blasts could be heard throughout the night because of the exchange of fire between the two sides,” the activist group said.

Originally a Syrian army base, Division 17 was seized by Daesh in 2014 when it took control of swaths of the wider Raqqa province.

The battle for the city is expected to be extended and bloody, and could mark a major turning point in the war against the militants.

Daesh 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.

The Daesh-linked Amaq 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.

Thousands have fled in recent months, and the U.N. humanitarian office estimates about 160,000 people remain in the city. They have no electricity and were facing severe water shortages, according to the activist collective known as Raqqa is Being Slaughtered Silently.The Observatory said coalition air strikes Saturday killed 24 civilians inside Raqqa, increasing the toll of civilian deaths in coalition raids to a total of 58 since the battle for city was launched on June 6.

In southern Syria, Jordan said its border guards have killed five suspected infiltrators in a pickup truck and two motorcycles approaching its frontier from Al-Tanf, a Syrian desert town where U.S. special forces training rebels are based. 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 statement did not give any details of the identity of the men and whether they were smugglers or militants in the area where Jordan’s northeastern borders meet both Iraq and Syria.

Al-Tanf has been a flashpoint in recent weeks as militias backed by Iran have tried to get near the U.S. garrison, prompting U.S. coalition jets to strike back. The town lies in the Syrian Badia, a vast sparsely populated desert territory that stretches to the Jordanian and Iraqi borders. Damascus has declared the Badia region a military priority.

Saturday, the Syrian army said its forces now hold more than a fifth of the country’s strategic desert, after reaching the eastern border with Iraq for the first time since 2015.