Antigovernment activists estimated that at least 33 people were killed in the artillery barrages on the Damascus suburb of Qudssaya aimed at the Free Syrian Army insurgents, less than three miles northwest of President Bashar al-Assad's official residence, and on Barzeh in northern Damascus, about three miles northeast.

Mr. Assad, in remarks to his cabinet reported by the official SANA news agency, did not explicitly acknowledge the proximity of the fighting, but said "we live in a state of war." As such, he said, "all our policies, directives and all sectors will be directed in order to gain victory in this war." Previously, he had characterized the 16-month-old uprising as a crime wave by foreign-backed terrorists.

In an apparently unrelated development, a Syrian Air Force lieutenant general was kidnapped by armed men from his home in Damascus, according to Syrian State Television, who identified him as Lt. Gen. Farage Shihada al-Maqat. He was abducted in the Adawi neighborhood of Damascus, an exclusive area where dignitaries and Russian advisers live. If the report is true, General Maqat would be the highest-ranking officer to be kidnapped or killed since the uprising began. More than 13 generals are among a wave of high-ranking officers who have defected to the opposition recently.

The developments came as the United Nations Security Council met in attempts to devise a new strategy on Syria, where diplomacy has repeatedly failed, and as Turkey, a supporter of the Free Syrian Army and other groups fighting to overthrow Mr. Assad, issued a new warning to Syria after the disputed downing of a Turkish warplane by Syria last Friday. Bolstered by unanimous support from Turkey's NATO allies, Prime Minister Recep Tayyip Erdogan said Syrian forces should avoid their shared border.

The assault in Damascus on the Republican Guard base began on Monday night and was intended as only a probing attack, according to a lieutenant of the Free Syrian Army whose unit carried it out and who was interviewed by Skype.

"It was not a big confrontation, it was just to test the Guards' capacity, for future attacks," said the lieutenant, who for security reasons asked to be identified only by his rank. "Our fighters were really surprised by the huge forces that immediately came and encircled the area."

As he put it, the incident proved that "one bullet in Damascus has more impact than a tank barrage in Idlib or Homs, because the regime doesn't hear the bombings but for sure they hear the bullet in Damascus."

Only 20 fighters with light weapons were involved, he said. "It was just a test for when the battle does move to Damascus."

The elite Republican Guard has about 8,000 soldiers and is devoted to the protection of Mr. Assad and his subordinates. The guard has also taken the lead in suppressing dissent in the capital area.

Other opposition sources reported an escalation of the fighting in Damascus, mainly from government shelling focused on the neighborhoods or suburbs of Qudssaya, Dummar and Al Hameh, all to the northeast of the Republican Guard base, which in turn adjoins the presidential palace.

The Syrian Observatory for Human Rights, an anti-Assad group in Britain with a contact network in Syria, reported that 10 people were killed in Qudssaya. The Local Coordination Committees, an anti-Assad group in Syria that has been documenting casualties in the conflict, reported 33 killed in Qudssaya, Al Hameh and Dummar, as well as 2 killed in the capital. The group also released a list of people it said were among 21 massacred by Syrian forces in Al Hameh.

The shelling early Tuesday was intense enough to be heard throughout the capital, according to Noor Bitar, who identified himself as the media coordinator for the Damascus branch of the Revolutionary Council Leadership, another anti-Assad group.

The fighting was confirmed in part by the official SANA news agency, which reported that "authorities clashed on Tuesday with armed terrorist groups in Al Hameh town in the Damascus countryside." The SANA report said the armed groups had blocked the old Beirut highway and officials had killed "tens of terrorists." Syria's official media refer to all anti-Assad activists as terrorists.

A woman who identified herself as Serene and who lives in the Mezze market area of Damascus, about three miles from the area of the heaviest shelling, said residents were awakened at 4 a.m. by the bombardment. "Everyone was up sending text messages wondering what was happening," she said, speaking by Skype. "We're used to car bombs, but this was shelling explosions. The circle is getting tighter."

Abu Rami, who lives in Qudssaya with his wife and two children, said people had been unable to go to work because of heavy shooting and bombardment. "The Free Syrian Army wants to move the battle to Damascus," he said. "We feel we live under a real war now, not just skirmishes here and there."

In Lebanon, gunmen erected roadblocks, burned tires and fired into the air in downtown Beirut in the predawn hours Tuesday, while in the suburb of Jounieh to the east, at least two land mines were found on the grounds of a hospital.

The roadblocks were manned by Shiites who apparently support Mr. Assad and who were angry over the arrest of a Shiite man suspected of firebombing and shooting into the offices of New TV, a Lebanon broadcaster that had criticized the Syrian government. The incidents aroused renewed concern that Lebanon's sectarian factions would again be dragged into the conflicts of its neighbor. Syria has close ties with Hezbollah and Amal, the dominant Shiite political parties here, and their activists have been strong supporters of Mr. Assad.

At the United Nations Security Council, which must decide in coming days whether to extend the mandate of a 300-member monitoring mission in Syria, diplomats were briefed in a private session by Hervé Ladsous, the undersecretary for peacekeeping, and Nasser al-Kidwa, a deputy of Kofi Annan, the special envoy to Syria representing the United Nations and Arab League, whose peace plan has been paralyzed. Operations of the monitors were suspended on June 16 because of the violence.

Mr. Annan has been seeking to organize a meeting this Saturday of what he has called countries of influence in the Syrian conflict, although it remains unclear how many may participate. Vitaly I. Churkin, the United Nations ambassador from Russia, the Syrian government's most important backer, told reporters that his country would attend.

Dalal Mawad contributed reporting from Beirut; an employee of The New York Times from Damascus, Syria; and Rick Gladstone from New York.