Foreign Minister Adnan Mansour slammed on Thursday officials who are demanding the government to expel the Syrian Ambassador Ali Abdul Karim Ali, noting that such a move violates diplomatic norms and conventions.

“We follow certain norms that we will not bend,” Mansour said in comments published in al-Joumhouria newspaper.

British Prime Minister David Cameron and U.S. President Barack Obama warned Wednesday they would be forced to consider a new course of action if Syria threatens to use chemical weapons on rebel fighters.

The two leaders agreed during a telephone call that "the use -- or threat -- of chemical weapons was completely unacceptable and would force them to revisit their approach so far," Cameron's Downing Street office said.

Syrian forces backed by helicopter gunships and tanks launched a deadly assault on parts of Damascus on Wednesday, activists said, as the regime battles to stamp out rebel resistance in the capital.

At least 37 people were reported killed in Damascus alone, a day after a top minister hinted that the embattled regime was ready to discuss President Bashar al-Assad's exit in any talks on ending the brutal 17-month conflict.

Four Lebanese nationals were killed and 10 others wounded in shelling by regime forces on the Syrian border town of Jousiyeh on Wednesday, media reports said.

“Four people who hail from Arsal were killed and 10 others wounded in the town of Jousiyeh on the Syrian side of the border,” the Beirut-based, pan-Arab television al-Mayadeen reported.

The United Nations on Wednesday called for greater international support to protect an increasingly divided Lebanon from fallout from the civil war in neighboring Syria.

Deadly clashes in Lebanon between supporters and opponents of Syria's President Bashar Assad have highlighted the need for international action, the U.N.'s political chief told the Security Council.

A journalist from the cultural section of the government daily Tishrin was shot dead Wednesday at his home in Damascus during a search operation by the army, his friends said.

"They were looking for Musab al-Odallah and killed him because he was close to the opposition. He was in charge of the cultural section of Tishrin. This is murder," said one of the friends when contacted by telephone.

The Islamic National Gathering agreed on Wednesday to a ceasefire in the clashes of the northern city of Tripoli that came into effect as of 5:30 p.m., but the fragile truce was shaken by intermittent gunfire that left two people dead and more than 10 wounded.

The initiative was supported by Prime Minister Najib Miqati and granted the army the right to respond to the sources of gunfire.

The Vatican's envoy to Syria Mario Zenari blamed both sides for violations in the conflict raging in Syria and called for humanitarian law to be respected in an interview aired on Wednesday.

"We have to demand that all sides in the conflict rigorously respect international humanitarian law which as we can see has fallen apart due to the fault of both warring sides," Zenari told Vatican radio.

France strongly condemned on Wednesday the clashes that erupted in the northern city of Tripoli between the rival neighborhoods of Bab al-Tabbaneh and Jabal Mohsen.

The French Foreign Ministry said in a statement: “The clashes are the result of historic disputes that have only been highlighted due to the developments in Syria.”

The March 14 general-secretariat urged the Lebanese government on Wednesday to file a complaint with the Arab League and the U.N. Security Council against Damascus for violating Lebanese sovereignty.

“Given the deteriorating situation in Lebanon, which warns of severe consequences, the March 14 forces ask the Lebanese government to file a complaint with the Arab League and the Security Council against the Syrian government for violating Lebanon’s sovereignty and stability,” the alliance’s general secretariat said following its weekly meeting.