BEIRUT >> Syrian rebels battled regime forces Monday in a heavily protected, upscale area of Damascus, activists said, in a sign that the country’s outgunned opposition is increasingly turning to insurgent tactics.

At least three people were killed in the firefight, which was the most serious clash in the Syrian capital since the uprising began a year ago. The battle with machine guns and automatic rifles brought the country’s violent conflict to the streets of a neighborhood that houses embassies and senior government officials.

The Britain-based Syrian Observatory for Human Rights, which has a network of activists throughout the country, said 18 government troops were wounded in the fighting and two later were believed to have died.

Rami Abdul-Rahman, who heads the Observatory, described the clash "as the most violent of its kind and closest to security centers in Damascus since the revolution began."

He said several "armed groups of defectors" came from one of the suburbs and fired a rocket-propelled grenade at the house of an army brigadier general. They then entered a building where they were chased by security forces.

It was not clear whether the general was hurt, he said.

The state-run SANA news agency gave a different version of events, saying the fighting broke out when security forces stormed an apartment used as a hideout by an "armed terrorist" group in the Mazzeh neighborhood.

The report said two gunmen were killed and a third was arrested while a member of the security forces was killed.

Due to restrictions on journalists in Syria, it was impossible to reconcile the two accounts. Since the start of the uprising against President Bashar Assad, the regime has referred to its opponents as terrorists and insisted the revolt is driven by a foreign conspiracy, not popular will.

The uprising began with mostly peaceful protests against the government, inspired by the Arab Spring uprisings across the region. But the regime cracked down violently, opening fire on demonstrations and rounding up thousands of protesters.

Russia, a key Assad ally, said the Syrian government and rebels should halt their fighting once a day to give the Red Cross access to the wounded. The call came after Russian officials met with the International Committee of the Red Cross, which had urged Moscow to take such a stand.

Russia had previously backed the ICRC’s call for a cease-fire, but Monday’s statement from the Foreign Ministry was worded more strongly than previous ones in an apparent signal that Moscow is raising the pressure on Syria.

A resident of the Mazzeh district of western Damascus said Monday’s two-hour clash began with an exchange of fire from automatic rifles and machine guns, and ended about 4 a.m. local time.

"We also heard three strong explosions," said the man, who spoke on condition of anonymity for fear of government reprisal.

He added that the clash was close to the Swiss Embassy and the home of Maj. Gen. Assef Shawkat, the deputy chief of staff for security affairs, who is married to Assad’s sister.

Mazzeh is home to affluent Syrians of different sects, and is the first Damascus neighborhood that people coming from Lebanon reach. It is about a mile (two kilometers) from a military airport.

An activist in the capital said the clashes were near the Political Security Directorate building and were followed by raids by security forces.

The rebel Free Syrian Army, which includes thousands of army defectors, has claimed responsibility for attacks against regime forces in the past, but the group’s leader, Col. Riad al-Asaad, refused to comment on Monday’s fighting.

"This is a sensitive military matter that we cannot comment about," he told The Associated Press by telephone from Turkey, where the movement is based.

Although armed rebels are active in the Damascus suburbs and satellite towns, they rarely venture into the capital, where Assad’s troops are deployed in force.

The fighting in Damascus comes after the rebels suffered several major setbacks when they were driven out of strongholds in the northern city of Idlib and the central city of Homs, in part because of the superior firepower from government forces.

Damascus has been largely spared the steady gunfire and killings reported elsewhere in Syria in the past year, although the capital has had several major bombings that targeted government security buildings.

The most recent attack was Saturday, when twin car bombs killed 27 people near the air force intelligence building and the criminal security department.

The bombings in Damascus and Aleppo have added a mysterious element to the anti-government revolt.

U.S. officials have suggested that al-Qaida militants may be joining the fray, perhaps exploiting the chaos.

Assad’s military has remained largely intact, making it a formidable opponent for the FSA, the most potent armed group challenging the regime. The FSA has struggled to acquire weapons, saying an influx of arms by foreign countries could help turn the tide.

But few are even considering arming the opposition, out of fear that it would make the conflict worse. Syria has a web of regional allegiances that extend to Iran and the Lebanese militant group Hezbollah, raising concern that violence could spread beyond its borders if other nations directly army the rebels or send in their own troops.

There also are fears of civil war, as the conflict has fed sectarian tensions.

The military’s top leadership is stacked heavily with members of the minority Alawite sect, to which Assad and the ruling elite belong. But Sunnis are the majority in the country of 22 million and make up the backbone of the opposition.

Diplomatic efforts to resolve the crisis have so far brought no result.

A team sent by the U.N.-Arab League envoy Kofi Annan is in Syria this week to discuss ways of implementing proposals to end the crisis.

During a recent visit to Damascus, Annan pushed for an immediate cease-fire to allow all parties to hold a dialogue on a political solution. The government responded in a letter to Annan that it is "keen to end violence" but insisted that rebels give up their weapons first.

The U.N. says more than 8,000 people have been killed in the yearlong uprising, which has deeply polarized a country where the Assad family has ruled for more than 40 years.

Russia has stood by Syria, providing Damascus with weapons even as the U.S., the European Union and others impose arms embargoes on the regime. Both Russia and China have protected Syria from U.N. sanctions, although Moscow recently has shown some signs that it was losing patience with Assad’s harsh stance.

Russian Foreign Minister Sergey Lavrov told lawmakers last week that the Syrian leader has been slow to implement long-needed reforms, warning that the conflict could spiral out of control.

He also complained in a weekend interview with Russian state television about the "unproportional" use of force by the government troops and said that Moscow disagrees with many of the decisions made by the Syrian leadership.

"We are supporting the need to start a political process, and to do that it’s necessary to have a cease-fire first," Lavrov said. "Russia will do everything for that, irrespective of the decisions made by the Syrian government. We disagree with many of those, by the way."

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Associated Press writer Vladimir Isachenkov contributed to this story from Moscow.