"Syrias disregard for its civilian population is all too evident in its air campaign, which now apparently includes dropping these deadly cluster bombs into populated areas," said Steve Goose, arms director at the New York-based group.

"Cluster bombs have been comprehensively banned by most nations, and Syria should immediately stop all use of these indiscriminate weapons that continue to kill and maim for years," he said in a statement.

HRW reported their increased use in the past week, notably in the Maaret al-Numan area where the armed forces have been locked in combat with Syria for control of the highway linking Damascus to the northern city of Aleppo.

But cluster bombs were also being dropped in the provinces of Aleppo, Homs, Latakia and Damascus, it said, basing its findings on videos posted online by Syrian activists.

"The cluster bomb canisters and submunitions shown in the videos all show damage and wear patterns produced by being mounted on and dropped from an aircraft," said HRW, although it did not have information on casualties.

"Human Rights Watch is deeply concerned by the risks posed by the unexploded submunitions to the civilian population, as men and even children can be seen in the videos handling the unexploded submunitions in life-threatening ways."

Syria has not ratified a convention banning cluster bombs that has been adopted by 109 countries since 2008.

The United Nations and Arab League peace envoy is currently on a regional tour aimed at finding a solution to the conflict in Syria after Damascus rejected a UN call to implement a unilateral ceasefire.

"During his visit, Lakhdar Brahimi will meet Iranian Foreign Minister Ali Akbar Salehi to discuss the situation in Syria," the channel quoted a foreign ministry statement as saying.

Iran, the main backer of Syrian President Bashar al-Assad, seeks a political solution to the conflict and supports the envoy's mediation efforts.

In Baghdad on Monday, Brahimi will meet Iraqi Prime Minister Nuri al-Maliki over the 19-month uprising, Maliki's spokesman said on Saturday.

"Iraq has said many times that it supports the efforts of Lakhdar Brahimi to find a solution, and we will work to make this mission successful to end the human tragedy of the Syrian people," Ali Mussawi said.

He said he had no further details on the veteran troubleshooter's schedule while in Iraq.

Brahimi first visited the Middle East in mid-September and met Assad in Damascus but earned no promise of concessions from him.

Brahimi visited Saudi Arabia on Wednesday and was in Turkey on Saturday.

In an interview with AFP on Tuesday, UN Secretary General Ban Ki-moon said Brahimi would return soon to Damascus to try again to meet Assad.

Ban suggested Brahimi could go to the Syrian capital next week if his meetings in the region this week were productive.