More than 23,000 people have been killed in violence in Syria since the outbreak of a revolt in March last year, the Britain-based Syrian Observatory for Human Rights said on Tuesday.

"As of August 13, 23,002 people were killed, including 16,142 civilians, 1,018 defectors and 5,842 soldiers," Observatory director Rami Abdel Rahman told Agence France Presse, adding that 2,409 people have been killed in the past 13 days alone.

The Turkish army on Tuesday staged a new military drill near its border with Syria, in the throes of an uprising that has led to deteriorating relations between the neighboring nations, the Anatolia news agency reported.

Turkish tanks accompanied by advanced armored personnel carriers and tactical missile-launching platforms were deployed at the Oncupinar crossing in southern Kilis province for the drill, the report said.

Syria's former prime minister, who defected last week, said Tuesday that the regime was collapsing and now only controlled about a third of the conflict-wracked country.

"The Syrian regime only controls 30 percent of Syria's territory. It has collapsed militarily, economically and morally," Riad Hijab told a news conference in the Jordanian capital.

A Syria-based reporter for Iran's Arabic language television network al-Alam has been abducted by rebels in the central Syrian city of Homs, the channel said on its website on Tuesday.

The journalist, named as Ahmed Sattouf, was taken by "armed terrorist groups" as he returned to his home in Homs, al-Alam said, using the term the allied regimes in Iran and Syria use to designate Syria's rebels.

U.N. humanitarian chief Valerie Amos arrived in Syria Tuesday to address the "deteriorating humanitarian situation" in the conflict-ravaged country and discuss ways of scaling-up relief efforts.

She will meet government officials and humanitarian partners including the local Red Crescent as well as families affected by the conflict, at the start of a three-day visit to both Syria and Lebanon, her office said in a statement.

Fresh fighting erupted Tuesday in Syria's second city Aleppo, where the army shelled several rebel-held areas, a rights watchdog said, after a bloody day in which 160 people were killed nationwide.

"Fighting broke out between government forces and rebel fighters in the (southwestern) districts of Saif al-Dawla and Salaheddin alongside explosions in the area," the Syrian Observatory for Human Rights said.

Hizbullah denied on Monday that the Free Syrian Army captured a member of the party in Damascus, Hizbullah's media relations department said.

“Al-Arabiya news channel reported that the FSA detained a member of Hizbullah identified as Sayyed Hassan Salim al-Meqdad. The party denies these claims,” said the statement.

Syrian National Council member Bassam al-Imadi stressed on Tuesday that the Syrian regime is “risking its most important cards” in Lebanon by tasking ex-Minister Michel Samaha with carrying out the terrorist plot targeting Lebanon.

President “Bashar Assad, who previously threatened to ignite the region, will not hesitate in sacrificing his allies in Lebanon,” al-Imadi told An Nahar newspaper.

Foreign ministers preparing for a summit in Mecca of the Islamic Cooperation Organization on Monday recommended the expulsion of Syria from the 57-nation bloc, its secretary general said.

Asked by reporters whether the foreign ministers had decided to call for a suspension after their meeting in the Saudi Red Sea city of Jeddah to prepare for Tuesday's summit, Ekmeleddin Ihsanoglu said: "Yes."

The United States said Monday it has not ruled out any option to bring about the departure of Syrian President Bashar Assad, following renewed speculation about a possible no-fly zone.

White House spokesman Jay Carney was asked about comments by U.S. Secretary of State Hillary Clinton in Turkey that sparked a new round of questions about a stepped-up Western role in the violence-wracked country.