Five Syrian White Helmets rescuers were killed on Saturday in an attack by masked gunmen in the northern province of Aleppo, the volunteer network said. The rescue force said armed men stormed its Al-Hader center in a pre-dawn attack and fired on the first responders inside. Four volunteers were killed on the spot and a fifth died later in hospital, it wrote on Twitter. "At around 2:00 am, an armed group stormed the Al-Hader center, blindfolded the staff members who were on the night shift, and killed five of them," said Ahmad al-Hamish, who heads the center. "Two others were wounded and another two were able to flee. The attackers were masked and escaped after stealing some equipment and generators," he said. It was unclear whether the attack was a robbery-gone-wrong or if the center and its crew had been specifically targeted. Founded in 2013, the White Helmets are a network of first responders who rescue wounded in the aftermath of air strikes, shelling or blasts in rebel-held territory. More than 200 White Helmets rescuers have been killed in Syrias seven-year war, usually in bombing raids or shelling on their centers. While attacks like the one on Saturday are rare, they have happened before. In August, seven White Helmets members were killed in a similar assault in the town of Sarmin, in neighboring Idlib province. On Saturday, five people were killed in a blast in the urban capital of the province, also called Idlib, according to the Britain-based Syrian Observatory for Human Rights. "Two were civilians, including a child. There was also one Uzbek fighter and two unidentified people," said Abdel Rahman. The explosion hit a wide street in Idlib lined by tall cement apartment blocks. Several cars parked outside had been burned by the explosion. White Helmets rescuers could be seen carrying several wounded out of the building, including a crying infant and a wounded man on a stretcher, to ambulances parked nearby. The killings come as the White Helmets are facing a "freeze" on funding from the United States, which is still reviewing over $200 million earmarked for stabilization in Syria.