The world is facing a "critical time", top U.S. diplomat John Kerry told China's President Xi Jinping on Saturday, citing tensions on the Korean peninsula, Iran's nuclear program and the conflict in Syria.

"Mr. President, this is obviously a critical time with some very challenging issues," Kerry told Xi in the Great Hall of the People in Beijing.

British military scientists have found forensic evidence that chemical weapons have been used in the conflict in Syria, the Times newspaper reported on Saturday.

A soil sample thought to have been taken from an area close to Damascus and smuggled back to Britain has provided proof that "some kind of chemical weapon" had been fired, it quoted defense sources as saying.

Israel's army fired artillery into Syria on Friday night after gunshots and shells were directed at soldiers on the Israeli-occupied sector of the Golan Heights, the military said.

"A short while ago, artillery and shots were fired at IDF (Israel Defense Forces) soldiers along the security fence between Israel and Syria," it said in a statement.

The families of the kidnapped pilgrims held in Syria staged a sit-in on Friday at Beirut's Martyrs' Square to demand the release of their loved ones.

They announced that they have launched a campaign to boycott Turkish products in Lebanon, urging citizens throughout the country to support them.

A major coalition of Islamist rebels fighting the regime of President Bashar Assad has denounced al-Nusra Front's pledge of allegiance to al-Qaida, urging insurgents to unite behind moderate Islam.

"When we in Syria launched our jihad (holy war) against the sectarian regime, we did not do so for the sake of allegiance to a man here or another there," said the Syrian Islamic Liberation Front (SILF) in a statement late on Thursday.

Western nations have "hard evidence" that chemical weapons have been used at least once in the Syrian war but a U.N. investigation is now unlikely to get into the country, diplomats said Thursday.

President Bashar Assad's government asked the U.N. to investigate its claims against rebel forces. But it is now refusing to let international experts into the country because the U.N. wants to look into claims against Assad's forces.

Syria's air force pounded a rural area near the eastern border town of Arsal for the second time in 24 hours on Thursday, officials said.

"I can confirm there was a raid," said Ahmad Fliti, deputy head of Arsal council.

Syria's economy and trade ministry plans to set up an office tasked with overseeing a boycott of Turkish industry, which has contributed to "sabotaging the national economy" an official said Thursday.

"Those factories that have contributed to sabotaging Syria's national economy and looting factories in Aleppo and its province... do not deserve to be dealt with as legal entities," Deputy Minister of Economy Abdel Salam Ali told Agence France Presse.

Syrian state television has confirmed that a video showing the March 21 killing of prominent religious cleric Mohammed Saeed al-Bouti is real, days after describing the footage as a fake.

In an unprecedented act, the broadcaster said it "apologized" for denying the authenticity of a video distributed online this week, showing the moment of an explosion in a Damascus mosque that killed Syria's best-known Sunni cleric.

Syrian regime forces are massing in the countryside of Qusayr city near Homs, backed by Hizbullah groups, in a bid to storm into the “strategic” Tal Qadesh area, a Syrian opposition member claimed on Thursday, urging Lebanon to stop “Hizbullah's interference in Syrian affairs.”

“Major reinforcements for Hizbullah and the Syrian army are massing in the western countryside of Homs and shelling with multiple rocket launchers and MiG warplanes intensified today in preparation for storming into the area and controlling Tal Qadesh,” Mouayed Ghizlan, member of the general secretariat of the opposition National Council, told CNNArabic.