BEIRUT (AP) -- An airstrike killed eight family members, five of them children, as they fled fighting between U.S.-allied Syrian forces and Islamic State militants on Monday, according to local activists, who said the strike appeared to have been launched by the U.S.-led coalition.
Al-Qaida's leader meanwhile urged his followers and other militants in Syria to unite and prepare for protracted jihad, or holy war, against what he called an "international satanic alliance," apparently referring to the Syrian government, its ally Russia, and the U.S., all of which are targeting the group.
The family was fleeing fighting in the northern Syrian town of Tabqa when their vehicle was struck, according to the Britain-based Syrian Observatory for Human Rights, which said the five children were between six months and 15 years old.
The activist-run Raqqa is Being Slaughtered Silently also reported the airstrike, saying a family was killed.
The US.-backed Syrian Democratic Forces, which also include Arab fighters, are trying to expel IS from Tabqa before moving on to Raqqa, the de facto capital of the jihadi group. Tabqa is 40 kilometers (25 miles) southwest of Raqqa.
The U.S. and its allies are believed to be the only forces flying missions over Tabqa. The Observatory said the U.S.-backed fighters entered Tabqa on Monday but the town remains largely under IS control.
The Islamic State group and al-Qaida have been bitter rivals since they split apart in 2013, with the former claiming to represent the world's Muslims in an apocalyptic showdown with the West and the latter fighting alongside the Syrian opposition.
Al-Qaida won allies among the opposition early in the civil war because of its military prowess. Al-Qaida's official branch, the Nusra Front, changed its name to the Fatah al-Sham Front and formally cut ties with al-Qaida last year, but is still widely seen as being linked to the global terror network.
In a recording released late Sunday, al-Qaida leader Ayman al-Zawahri called on Syria's various jihadi factions to unite in order to wage guerrilla war.
He cast the Syrian conflict as part of a wider struggle aimed at imposing Islamic rule on the region and beyond. The local leaders of the Fatah al-Sham Front have tended to portray its struggle as being confined to Syria.
The Fatah al-Sham Front is perhaps the most powerful rebel-aligned faction, but dozens of other factions - both hard-line Islamists and more mainstream groups - are also battling Syrian President Bashar Assad's forces. Fatah al-Sham Front is the commanding faction in Idlib, the rebel-held province in northwestern Syria.
Zawahri, who became the global leader of al-Qaida after Osama bin Laden was killed in a U.S. raid in 2011, made his last public broadcast in May 2016, when he issued an audio message calling for unity among fighters in Syria.
Meanwhile, authorities began a sixth round of evacuations on Monday for civilians and fighters from the opposition-held neighborhood of al-Waer in Homs, Syria's third largest city, activists and Syrian state media reported.
Government forces have besieged the neighborhood since 2013, according to the Washington-based monitoring group Siege Watch. Rebels, opposition activists and their families agreed to vacate the district in an agreement signed in March in exchange for the end of hostilities. The government will retake control of the neighborhood after the last of twelve rounds of evacuations are complete, in an expected three to four weeks, according to local media activist Osama Abou Zeid.
He said about 16,000 people are expected to leave the neighborhood, instead of reconciling themselves with the government's notorious security services. Siege Watch estimates there have been 60,000 people trapped under the siege.
An estimated 1,800 people, including some 500 fighters, left on Monday, said Abou Zeid. They are being taken to Jarablus, a town on the Turkish border that is under the control of Turkish troops and Syrian opposition forces.
Tens of thousands of people living in besieged areas around Damascus, Homs, and Aleppo - Syria's largest city - have surrendered after prolonged sieges in exchange for safe relocation to opposition-held areas elsewhere in the country. Another 8,000 people have left two pro-government towns in northern Syria, which were besieged by rebels.
Critics say the population transfers are redrawing Syria's map along sectarian and political lines.
In northern Syria, warplanes struck the town where a chemical attack that was widely blamed on government forces killed nearly 90 people earlier this month. The government has denied using chemical weapons.
The airstrikes in the opposition-held northern town of Khan Sheikhoun killed at least four people and wounded 10 others, according to the activist-run Thiqa News Agency and Edlib Media Center. It was not immediately clear who carried out the strike.
The Britain-based Syrian Observatory for Human Rights said at least five people, including a child, were killed in the attack on a vegetable market.
Associated Press writers Maamoun Youssef in Cairo and Hashem Osseiran in Beirut contributed to this report.