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Syrian activists and a Kurdish news agency say a suicide bomber has struck a wedding hall just outside the northeastern Syrian city of Hassakeh.

The Britain-based Syrian Observatory for Human Rights, which relies on a network of activists inside Syria, says the attack killed 14 people, with the toll expected to rise. The Kurdish Hawar news agency confirmed the attack but did not provide a toll.

Syrian Kurdish forces control most of the Hassakeh province, but the Syrian government maintains some strongholds there.

Islamic State militants have repeatedly targeted the Kurds, who have proven to be among the most effective ground forces battling the extremist group.

An al-Qaida-linked group in Syria says one of its senior commanders, who was close to al-Qaida's top leader Ayman al-Zawahri, has been killed in an airstrike.

Monday's announcement by the Fatah al-Sham Front, formerly known as the Nusra Front, came shortly after the Pentagon said the U.S. had targeted a prominent member of the group in Syria. Navy Capt. Jeff Davis would not provide further details.

A Twitter account run by the group says Ahmed Salama Mabrouk, a veteran Egyptian jihadist known as Abu Farag al-Masri, was killed in a U.S.-led coalition airstrike in the northern Idlib province, which is controlled by an insurgent alliance that includes the Fatah al-Sham Front.

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A suicide bomber struck a Syrian wedding (AP)

The Britain-based Syrian Observatory for Human Rights, which relies on activists inside Syria, says Mabrouk was killed when his vehicle was hit near the border with Turkey.

Mabrouk was imprisoned in his native Egypt in 1981 in the sweep following the assassination of President Anwar Sadat. He later traveled to Afghanistan, where he became close to al-Qaida's leader al-Zawahri before traveling to Syria.

A Syrian monitoring group says more than 400 civilians have been killed in and around the northern city of Aleppo since a U.S-and Russian-brokered cease-fire collapsed two weeks ago.

The Britain-based Syrian Observatory for Human Rights says Monday that Russian and Syrian warplanes, and government artillery, has killed at least 387 civilians in the besieged rebel-held eastern Aleppo and its rural surroundings, including 72 children and 24 women. Most were killed inside the city.

The short-lived cease-fire, which collapsed Sept. 19, was followed by an intensive bombing campaign that hit infrastructure, hospitals and water stations in the besieged eastern part of Aleppo, which houses 275,000 people.

Government forces also launched a limited ground operation into eastern Aleppo, which was captured by the rebels in 2012.

The Observatory says the opposition has shelled the adjacent government-held neighborhoods of western Aleppo, killing 19 people, including five children and seven women. It says the total number killed in and around the city is 406.

Turkey says its participation in possible offensives to free Islamic State-held strongholds in Mosul in Iraq and Raqqa in Syria would be conditional upon the exclusion of Syrian Kurdish forces from the operations.

Deputy Prime Minister Numan Kurtulmus, told reporters Monday that "one of the basic conditions for Turkey's participation in these operations is for the PYD and YPG not to be included."

He was referring to the People's Protection Units, the YPG, and its political arm, the Democratic Union Party, or PYD.

The United States regards the Syrian Kurds as one of the most effective front-line forces in the battle against IS. Ankara considers them terrorists because of their affiliation to Kurdish separatists in Turkey and opposes their territorial expansion in northern Syria.

On Monday, Kurtulmus reiterated a Turkish demand that all Syrian Kurdish forces, which liberated the IS-held Manbij region in northern Syria this summer, retreat to the east.

He says "an important number have retreated," but "elements are still present, and we are once again requesting that the United States keeps to its promise and ensures that the PYD/YPG elements move east of the Euphrates (River)."

Syria activists say warplanes have once again targeted one of the largest trauma and emergency hospitals in the besieged, rebel-held part of Aleppo, this time rendering it "not salvageable."

Adham Sahloul, of the U.S-based Syrian American Medical Society, which supports the hospital, says a bunker-busting bomb punched a 10-meter-deep crater where it landed Monday at the hospital's front entrance.

Sahloul says at least three maintenance staff were killed, including one found 100 meters (330 feet) away, apparently thrown by the impact of the explosion.

The hospital has been targeted twice in the last week.

The Britain-based Syrian Observatory for Human Rights confirmed the bombing, but put the death toll at six.

Sahloul says most of the hospital's facilities were set up underground to protect it. He says there are fears the rest of the building could collapse. Rescue workers are still searching for people under the rubble.

The IS-linked Aamaq news agency reports that the extremist group has claimed responsibility for suicide attacks in the central Syrian city of Hama that killed two people and wounded 12.

The attack was carried out by two suicide bombers wearing explosives-laden belts near the ruling Baath party office and a police station, Aamaq reported on Monday.

Syria's state news agency SANA reported earlier in the day that two suicide bombings had struck the central city of Hama killing two people and wounding at least 12.

SANA said a suicide bomber detonated his explosives-packed belt in al-Assi Square in Hama city, and that the other suicide bombing occurred 15 minutes later.

Hama is Syria's fourth-largest city and has seen relatively little fighting in recent years as the country's conflict rages on. It is firmly under the control of Assad's forces.

Syrian state TV says a suicide attacker wearing an explosives belt has blown himself up on a main square in the central city of Hama, causing an unspecified number of casualties.

The TV says the attack occurred on Monday near the busy Assi Square in Hama. It gave no further details.

The Britain-based Syrian Observatory for Human Rights says two explosions were heard in Hama.

Hama is Syria's fourth largest city and has been relatively quiet in recent years. It is firmly under the control of President Bashar Assad's forces.

The suicide attack came as insurgent groups have been on the offensive north of the city, which is the capital of the province that carries the same name.