BEIRUT (AP) -- Syrian warplanes and artillery blasted parts of the capital Damascus and its rebellious suburbs on Sunday, part of what activists described as intense fighting as rebels try to push their way into the center of President Bashar Assad's power base.

In central Syria, a car bomb killed at least 15 people, the official news agency reported.

The fighting over the past few weeks in Damascus is the most serious in the capital since July, when rebels captured several neighborhoods before a swift government counteroffensive swept them out.

The Britain-based activist group Syrian Observatory for Human Rights said fighter jets struck twice in the suburb of Daraya as regime artillery pounded other districts just south of Damascus.

The Syrian air force also launched airstrikes on the northern city of Aleppo, some cities in the northern province of Idlib and the Mediterranean city of Latakia, the Observatory said. The group relies on reports from activists on the ground.

The Damascus suburbs have been opposition strongholds since the uprising against Assad began in March 2011. In the past weeks, the army has pressed an offensive to regain lost territory near the capital, including two air bases. The Observatory said there was also ongoing fighting in towns near the Damascus International Airport on the southern edge of the city. The towns include Aqraba, Beit Saham and Yalda.

The road to the airport from Damascus was closed on Thursday because of heavy fighting, but authorities reopened it after troops secured the area, activists said. The Information Ministry said on Saturday the airport was operating normally and that the road leading to the facility is "totally secure."

On Sunday, EgyptAir Chief Executive Roshdy Zakaria said the country's national carrier will resume flights to Damascus and Aleppo after a three-day suspension because of poor security on the roads around the two airports.

In central Homs province, a car bomb exploded near Omar Bin al-Khattab mosque in the al-Hamra neighborhood of Homs, killing at least 15 people and wounding 24, state-run SANA news agency said.

Activists said seven people died in the attack. The Observatory said the death toll is likely to rise because some were critically wounded.

There was no immediate claim of responsibility.

In a village just outside Homs, two other people were killed by artillery shelling, including a baby girl, the Observatory said.

Homs has been a frequent battleground in the 20-month rebellion aimed at toppling Assad.

The increase in bombing attacks as part of the civil war has raised concerns that Islamist extremist groups are taking a larger role on the side of the rebels.

SANA claimed that on the outskirts of Homs, the Syrian army killed scores of rebels in an attack on their hideouts.

Activists say at least 40,000 people have been killed in the conflict, which began with peaceful pro-democracy protests but turned into a civil war.

While fighting has intensified nationwide in the past weeks, members of the new Syrian opposition leadership coalition held talks in Egypt on a transitional government.

The Syrian National Coalition for Opposition and Revolutionary Forces was established earlier this month in Qatar under pressure from the United States for a stronger, more united opposition body to serve as a counterweight to the more extremist forces which have joined the fight against Assad's regime -- some of them foreign jihadists.

The coalition members said they have agreed on the framework of a transitional government with 10 ministers. Walid Albunni, the coalition's spokesman, said its members will speed up the decision-making process and name the prime minister in the coming days to keep up with developments on the ground.

"We have to work as fast as possible to be ready for the downfall of the regime," Albunni said Saturday at the end of a three-day meeting in Cairo, where the opposition body is based.

Albunni said the coalition could support a United Nations peacekeeping force in Syria, but only after Assad is toppled.

"Anything can happen after all those who have stained their hands with blood of people are gone," Albunni said.

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Associated Press writer Aya Batrawy in Cairo contributed to this report.