Syrian security forces killed six civilians on Tuesday during a raid on anti-government protesters amid reports the United States expects the fall of President Bashar Assad and more violence after.

Meanwhile, an activist group inside Syria announced its backing for a recently named National Council of opposition figures, underscoring the need for unity in the campaign to overthrow the regime.

The Mustaqbal parliamentary bloc on Tuesday voiced concerns over “the recurrence of security incidents” in the country.

In a statement issued after its weekly meeting, the bloc said it discussed “the surge in security incidents, such as the latest atrocious crime against the peaceful family of Ali al-Hajj Dib in the Ras al-Nabaa area, and other daily incidents involving the use of firearms.”

Two civilians were killed on Tuesday when Syrian security forces opened fire during a raid targeting anti-regime protesters in the central flashpoint city of Homs, rights activists said.

"Two civilians were killed in the Baba Amr neighborhood. Other residents were seriously hurt in Homs, where gunfire was heard from Monday night in many neighborhoods," the Britain-based Syrian Observatory for Human Rights said, without giving further details.

The United States is increasingly convinced Syrian President Bashar al-Assad will be overthrown and is preparing for a possibly violent aftermath, the New York Times reported Tuesday.

The newspaper said Washington is quietly working with Turkey to plan for a post-Assad future that could see Syria's various ethnic groups battle for control of the country, potentially destabilizing neighboring states.

Hizbullah deputy leader Sheikh Naim Qassem accused the March 14 forces on Tuesday of acting in a way that serves the U.S.-Israeli project.

“I don’t like to mention much what the March 14 group is doing as a conspiracy,” Qassem told Iran’s Fars news agency. “But it acts in a way that whether willingly or unwillingly serves the Israeli-American project.”

The Internal Security Forces killed two accomplices of the alleged mastermind behind the kidnapping of seven Estonians during clashes in the area of al-Bireh in Rashaya at midnight, media reports said Tuesday.

The National News Agency said the two men were killed at around 12:30 am after the ISF put iron barricades on a road between al-Bireh and Izza to stop their four-wheeler. But their vehicle veered off its course and hit a wall.

U.S. Secretary of State Hillary Clinton on Monday urged Russia to support a "strong statement" at the U.N. Security Council over Syria's crackdown on protests, senior U.S. officials said Monday.

In her talks with Russian Foreign Minister Sergei Lavrov, Clinton expressed "our interest in seeing the Security Council go on record with a strong statement on Syria," a senior administration official said on condition of anonymity.

The Syrian regime's bloody crackdown on protestors is intensifying, the U.N. human rights office said Monday as it called for a global response to alleviate the "dire situation" in Syria.

"Despite the mounting international pressure in the past six months since the start of protests, ... the bloody crackdown in Syria has intensified," U.N. Deputy High Commissioner for Human Rights Kang Kyung-wha said.

A Syrian judge freed opposition figure Georges Sabra on Monday, almost two months after he was arrested at his home in Qatana near Damascus, his lawyer said.

"The judge decided to release Georges Sabra today after questioning on charges that were brought against him," said the lawyer Khalil Maatuk.

Syria's security forces opened fire on Monday during a raid on political dissidents in the town of Houla in central Homs province, a flashpoint in the months-long anti-regime uprising, activists said.

"Five residents, including a woman, were shot dead on Monday by security forces, who have been conducting a sweep in Houla since Sunday," the Syrian Observatory for Human Rights said in a statement.