BEIRUT  - Fresh battles broke out in a flashpoint district of Aleppo on Monday, while violence raged on the road linking the Syrian city to its international airport, a watchdog said.

"Fierce clashes raged between troops and rebels in the east of Sheikh Maqsud district," said the Syrian Observatory for Human Rights, a day after a major rebel advance in the predominantly Kurdish neighbourhood.

Regime tanks fired shells at other parts of the neighbourhood, whose residents fled the area in large numbers for a second straight day.

Southeast of Aleppo, fresh clashes broke out near the city's international airport, said the Observatory, which relies on a network of activists, doctors and lawyers across Syria for its reports. The airport has been closed since January. Aleppo city has been scene of some of Syria's fiercest violence since battles first broke out in the northern city in July last year.

Much of the city has since been destroyed, and residents suffer constant power cuts and frequent water shortages. To the west of the city, an air strike on rebel-held the town of Maaret al-Numan killed at least one child, said the Observatory, which reported several others injured.

Located in the northwestern province of Idlib, Maaret al-Numan has been under rebel control since October last year. Elsewhere, a blast caused by an explosive device hit the Rokn Eddin district in northern Damascus, said the Observatory, which also reported renewed shelling by government troops on rebel-held districts in the central city of Homs.

Monday's violence comes a day after at least 181 people were killed across Syria, among them 57 rebels, 67 civilians and 57 loyalist troops, the Observatory reported. The UN says more than 70,000 people have been killed in Syria's two-year war.

Meanwhile, unknown attackers kidnapped nine members of Syria's Alawite community on Monday after they crossed into Lebanon by bus, a security official said.

The assailants seized the group "shortly after their bus crossed the Syrian-Lebanese border via the Jisr Aqmar crossing into the Wadi Khaled area of north Lebanon," the official told AFP on condition of anonymity. "Women and children were among the group," the official added, without giving any further details.

Two years into a spiralling war in neighbouring Syria, sectarian tensions have flared up in Lebanon. Frequent sectarian clashes have raged in the flashpoint city of Tripoli in northern Lebanon, where Alawite fighters have battled armed members of the Sunni community.

Last week, a wave of tit-for-tat kidnappings hit eastern Lebanon, pitting Shiites against Sunnis. Damascus dominated Lebanon militarily and politically for nearly 30 years until 2005, when Syrian forces withdrew from the country under international pressure.

The country's Sunni-led March 14 political movement supports Syria's rebels, while the powerful Shiite movement Hezbollah and its allies back Syrian President Bashar al-Assad, an Alawite whose faith is an offshoot of Shiite Islam.

Meanwhile, the Syrian Observatory for Human Rights said on Monday that March was the bloodiest month yet in Syria's two-year conflict, with more than 6,000 people killed, a third of them civilians.

The group opposes President Bashar al-Assad but has monitored human rights violations on both sides of a revolt that began as peaceful protests but is now a brutal war between forces loyal to Assad and an array of rebel militias.

The Britain-based Observatory, which has a network of sources across Syria, has documented 62,554 dead in the conflict, said Rami Abdelrahman, the head of the group.

"But we know the number is much, much higher," he told Reuters by telephone. "We estimate it is actually around 120,000 people. Many death tolls are more difficult to document so we are not officially including them yet."

As in previous months, around a third of those killed in March were civilians, the Observatory said. Almost 300 children died, taking the number killed in the conflict to around 4,390.

The United Nations says more than 70,000 people have died in Syria. Abdelrahman said both sides have found ways to minimize their dead to keep morale high among their followers.

"There are some groups where it took us longer to get access to sources. For example we started counting deaths much later among the shabbiha," said Abdelrahman, referring to pro-Assad militias that have fought alongside security forces.

His group has a rough count of 12,000 dead shabbiha fighters but has yet to include those in its toll.

Also unknown is the number of dead among the tens of thousands jailed by Assad's forces since the conflict began. There was also no way to count the number of Syrian soldiers killed after being captured by rebels. Activists believe those are also likely to number in the thousands.

Some 2,250 dead opposition fighters are unknown, and the Observatory said it believed most of those are fighters from abroad who joined the rebels in Syria, which has become a site for jihad, or "holy war", to many Islamic militant groups.

Assad has long accused his opponents of being "terrorists" funded by Gulf and other foreign powers.

Disunity among the opposition in exile and the armed factions on the ground has hindered the struggle against Assad and contributed to Western reluctance to intervene.

Abdelrahman called on foreign powers to take action to help ease Syria's crisis as violence continues to rise.

"It seems that Bashar al-Assad is satisfied killing as much as needed to keep his throne. But it also seems that Syrian blood is of no value to Arab or Western powers who have been making promise after promise, while Syrians are led to slaughter," he said.