BEIRUT — The death toll in Syria’s three-year conflict has exceeded 150,000, an activist group said Tuesday as fighting raged across the country, including an attack in the north that killed at least 31 people including 9 children.

The Britain-based Syrian Observatory for Human Rights said that it has documented 150,344 deaths in the conflict that started in March 2011. The figure includes civilians, rebels, and members of the Syrian military. It also includes militiamen, fighting alongside President Bashar Assad’s forces and foreign fighters battling for Assad’s ouster on the rebels’ side.

Additional Photos

This Aug. 21, 2013, file image provided by Shaam News Network, which has been authenticated based on its contents and other AP reporting, purports to show bodies of victims of chemicals attack on Ghouta, Syria. The Britain-based Syrian Observatory for Human Rights said Tuesday that it has documented 150,344 deaths in the conflict that started in March 2011. The figure includes civilians, rebels, and members of the Syrian military. It also includes militiamen, fighting alongside President Bashar Assad’s forces and foreign fighters battling for Assad’s ouster on the rebels’ side. The Associated Press/Shaam News Network

In this Jan. 29, 2013, file photo, a man walks past dead bodies in front of a river in the neighborhood of Bustan al-Qasr in Aleppo, Syria. The Britain-based Syrian Observatory for Human Rights said Tuesday that it has documented 150,344 deaths in the conflict that started in March 2011. The figure includes civilians, rebels, and members of the Syrian military. It also includes militiamen, fighting alongside President Bashar Assad’s forces and foreign fighters battling for Assad’s ouster on the rebels’ side. (AP Photo/Abdullah al-Yassin, File) The Associated Press

The Observatory bases its tally on the information the group receives from a network of informants on the ground inside Syria.

In January, the U.N. said it had stopped updating its own tally of the Syrian dead because it can no longer verify the sources of information that led to its last count of at least 100,000 in late July.

Of the 150,344 people who died in the conflict, about a third, 51,212, were civilians, including 7,985 children and 5,266 women, The Observatory said. The number also includes 26,561 rebel fighters and 35,601 Syrian soldiers as well as 22,879 Assad-loyal fighters and 11,220 foreign fighters battling on the opposition side. The number also includes unidentified casualties totaling 2,871.

Tuesday’s attack in the northern town of Maaret al-Artiq came in the form of a barrel bombing — bombardment with containers stuffed with explosives rolled out of military helicopters, the Observatory said.

In Turkey, the Syrian’s main opposition bloc said its President, Ahmad al-Jarba, made a rare visit to Syria on Tuesday, meeting with rebels fighting Assad’s troops in the coastal province of Latakia — including the recently captured Christian-Armenian town of Kassab.

Assad’s family hails from Latakia, the scene of a fierce 11-day battle in which rebel groups including the al-Qaida-linked Nusra Front have made significant gains. So far, they’ve captured a border crossing with Turkey and a tiny slice of the coast that gives them access to the Mediterranean Sea.

In addition to Kassab, al-Jarba also toured Latakia’s rebel-held mountainous areas of Jabal al-Turkomen and Jabal al-Akrad, meeting with rebel commanders to assess the “latest plans and needs for the battle on the coast,” the Western-backed Syrian National Coalition said in a statement.

Syria’s uprising began with largely peace protests against Assad’s rule. It has since then evolved into a civil war with sectarian overtones, pitting predominantly Sunni Muslim rebels against Assad’s government that is dominated by Alawites, a sect in Shiite Islam. On the opposition side, Islamic extremists, including foreign fighters and Syrian rebels who have taken up hard-line al-Qaida-style ideologies, have played an increasingly prominent role among fighters, dampening the West’s support for the rebellion to overthrow Assad.

That has led to a backlash by Islamic brigades and more moderate rebels who launched a war against the al-Qaida breakaway group, the Islamic State of Iraq and the Levant. Infighting has raged in the north for months and more than, 3,000 fighters have been killed in the rebel-on-rebel violence since the beginning of the year, according to activists. These deaths were not included in Observatory’s tally.

On Tuesday, The Observatory said fighting between Assad’s loyalist and the rebels was concentrated in several opposition-held suburbs of the capital, Damascus, and the northern province of Aleppo, where rebels have managed to hold on to large swaths of territory and whole districts of the city of Aleppo, Syria’s largest urban center and its commercial hub. The rebels captured them from government forces in a 2012 offensive.

The group also reported heavy clashes in the southern province of Daraa that is the birthplace of Syria’s uprising.

Syria’s official SANA news agency said terrorists, a term state media uses for rebels, have fired mortars into a government-held district of Aleppo, killing five people and wounding 26 others. In Damascus, one person died and two were injured in separate mortar attacks on the capital’s districts of Zablatani and Abassyeen, SANA said.