The leader of the Islamic State group Abu Bakr al-Baghdadi on Thursday urged Muslims to emigrate to his self-proclaimed "caliphate", in the jihadist supremo's first audio recording in six months.

"And we call upon every Muslim in every place to perform hijrah (emigration) to the Islamic State or fight in his land wherever that may be," he said.

Jihadists from the Islamic State group executed 26 civilians on Thursday after overrunning their villages near Syria's ancient city of Palmyra, the Syrian Observatory for Human Rights said.  

"Daesh executed 26 civilians, including at least 10 by beheading, after accusing them of collaborating with the Syrian regime," said Observatory head Rami Abdel Rahman, using the Arabic acronym for IS.

The Loyalty to the Resistance bloc urged on Thursday support for Hizbullah and "its mission of confronting foreign aggression."

MP Hassan Fadlallah said after the bloc's weekly meeting: “The battle that Hizbullah is waging in al-Qalamoun is a national duty obligated by the interests of our people.”

Iran's military and financial support to Syria's regime is unwavering, a high-ranking Iranian official said in Damascus Thursday, calling a U.S. program to train Syrian rebels "a strategic mistake".

"We came to Syria to announce that our support for the Syrian regime is firm and eternal," said Alaedin Boroujerdi, head of the Iranian parliament's national security and foreign policy, at a press conference concluding his two-day visit.

Regime air strikes on three adjacent rebel-held villages in northern Syria killed at least 39 civilians, 17 of them children, a monitoring group said on Thursday.

Eight siblings were among the dead from the Wednesday strikes in southern Aleppo province, around 15 kilometers (10 miles) from the main highway south towards the capital, the Syrian Observatory for Human Rights said.

Progressive Socialist Party leader MP Walid Jumblat criticized on Thursday the sentence issued by the military court against former Minister Michel Samaha.

“The court's verdict in Samaha's case legalizes assassinations and explosions,” he said in a statement.

Pakistan's biggest city of Karachi was brought to a standstill Thursday following the massacre of 44 minority Shiite Ismaili Muslims in the first attack officially claimed by the Islamic State group in the country.

Hundreds of distraught relatives lined the streets around a cemetery in the city's eastern Safoora Goth area passing the coffins of the men and women who were killed on Wednesday when up to six gunmen stormed a bus and shot them in the head and upper body.

Thousands of Hizbullah fighters are engaged in the battle in the Syrian region of Qalamoun as the party's leadership is seeking to boost its capabilities and improve its performance to control the area along with the Syrian Army forces.

“Thousands of fighters, who hail from various Lebanese towns, are participating in the war raging in al-Qalamoun,” prominent Hizbullah sources told the Kuwaiti al-Rai newspaper on Thursday.

Syria's security services chief Ali Mamluk attended a meeting between President Bashar Assad and an Iranian official on Wednesday, after a newspaper claimed he was under house arrest for plotting a coup.

Mamluk's presence at the meeting, which was reported by the official news agency SANA, came after Britain's Telegraph newspaper said the top regime official had been sidelined.

Hizbullah and the Syrian army seized control Wednesday of the strategic Tallet Moussa hill in Syria's Qalamoun, as they pressed on with a major offensive against militant groups in the border region.

“The Syrian army and the fighters of the resistance (Hizbullah) have taken the strategic Tallet Moussa hill in Qalamoun,” Hizbullah's al-Manar television reported.