(CNN) -- Syria's leading opposition group has reached an initial agreement with other factions to form a new, inclusive body that could transition into a new government, a move widely seen as necessary in the effort to oust President Bashar al-Assad.
The Syrian National Council was under pressure by the United States and Arab nations, primarily Qatar, to unite with various other opposition groups. Talks over the issue continued Sunday in the capital of Doha.
"We have entered into open dialogue with our brothers in the Syrian opposition," said George Sabra, the head of the SNC.
"We heard from them and we studied the initiatives that they presented. We also have our point of view and thoughts that we will present, but we are serious enough to work toward the unity of the opposition as a central issue," Sabra explained, adding that the SNC wants to help build the new organization on solid ground.
Syrian opposition figure Ali Sadr Aldeen al-Bayanouni, the former top official with the Muslim Brotherhood in Syria, announced that all opposition forces agreed to establish the national coalition, and that the accord would be officially signed Sunday evening, Qatar's official news agency reported. When the deal is signed, the group will also select its leadership.
The move comes as fighting between government and rebel forces escalated amid reports that al-Assad is losing his grip on the country that his family has ruled for more than four decades.
Under the proposal put forward, the council would become part of a new opposition group that would set up a de facto government inside rebel-held areas of Syria.
The Syrian Human Rights Network -- al-Assad's answer to the opposition-linked rights groups the Local Coordination Committees of Syria and the Syrian Observatory for Human Rights -- accused the countries supporting the opposition conference in Qatar of sponsoring terrorism.
Al-Assad has refused to acknowledge the civil war, saying repeatedly his government is fighting foreign-backed "terrorists" bent on destabilizing the country.
The nearly 20-month conflict in Syria has its roots it the success of popular uprisings in Egypt, Tunisia and Libya, with Syrian demonstrators taking to the streets echoing the calls of Arab Spring protesters for political reform and political freedoms. The violence has taken hold of towns in the north, forcing thousands of Syrians to flee across the border into Turkey.
Al-Assad ordered a brutal crackdown against demonstrators, a move that spawned an armed uprising that has since devolved into a civil war.
At least 30 people were killed in fighting across Syria Sunday, the LCC reported. At least 13 of them were killed in Damascus and its suburbs.
More than 35,000 people are believed to have been killed in the fighting, and more than 400,000 people have been displaced, according to opposition and United Nations estimates.
Conflict spills over border with Israel
Israel fired warning shots toward Syria Sunday after a mortar shell hit an Israeli military post -- the first time Israel has fired on its neighbor across the Golan Heights since the 1973 Yom Kippur War.
The shell from Syria hit an IDF post in the Golan Heights adjacent to the Israel-Syria border, "as part of the internal conflict inside Syria," an Israeli military spokeswoman said.
Israel has filed a complaint through U.N. forces operating in the area, "stating that fire emanating from Syria into Israel will not be tolerated and shall be responded to with severity," the IDF said.
It's the fourth such complaint Israel has filed, though so far no one in the Golan Heights area has been injured.
"We interpret it as pinpoints leaks into Israel territory. It's totally internal conflict in Syria. We believe that Israel is not the target here. We are looking at either stray bullets or stray mortars," said Israeli Lt. Col. Avital Leibovich said.
The Golan is regarded internationally as occupied territory despite Israeli governmental control. It is home to 41,000 residents -- Jewish settlers, Druze and Alawites themselves. Israel seized the territory from Syria during the 1967 Israel-Arab war, and it was eventually annexed.
CNN's Raja Razek in Beirut contributed to this report.
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