BEIRUT — U.N. observers investigating a reported mass killing in a Syrian village on Saturday found pools of blood in homes and spent bullets, mortars and artillery shells, adding details to the emerging picture of what anti-regime activists have called one of the deadliest events of Syria’s uprising.

Dozens of people have already been buried in a mass grave, and activists are still struggling to determine the total number of people killed in what they say was a violent bombardment by government tanks and helicopters this week.

Some of the emerging details suggested that, rather than the outright bombing of civilians that the opposition has depicted, the violence in Tremseh may have been a lopsided fight between the army pursuing the opposition and activists and locals trying to defend the village. Nearly all of the dead are men, including dozens of armed rebels. The U.N. observers said the assault appeared to target specific homes of army defectors or opposition figures.

Running tolls ranged from 103 to 152, including dozens of bodies buried in neighboring villages or burned beyond recognition. The activists expected the number to rise since hundreds of residents remain unaccounted for, and locals believe bodies remained in nearby fields or were thrown into the Orontes River.

The Tremseh violence appeared to be one of the bloodiest events in the now 16-month-old uprising against President Bashar Assad, in which activists say more than 17,000 people have been killed so far. The new deaths brought intensified international condemnation of his regime, and the Turkish prime minister added his voice to the chorus Saturday.

“These vicious massacres, these attempts at genocide, these inhuman savageries are nothing but the footsteps of a regime that is on its way out,” Recep Tayyip Erdogan said. “Sooner or later, these tyrants with blood on their hands will go and the people of Syria will in the end make them pay.”

On Saturday, an 11-vehicle team of U.N. observers entered Tremseh, home to between 6,000-10,000 residents and one of a string of small farming villages along the Orontes River northwest of the city of Hama.

Based on its investigation, the team said in a statement that “an attack” took place on July 12. It said the violence seemed to target the homes of army defectors and activists, some of which were burned or damaged and had pooled or splattered blood and bullet casings inside.

The team also found evidence of artillery shells and mortars, which only government troops have, as well as assault rifles, the staple of Syria’s rebels.

It did not give a casualty figure but said the team would return Sunday to continue investigating.

Independent verification of the events in nearly impossible in Syria, one of the Middle East’s strictest police states, which bars most media from working in the country. The observers are in the country as part of an all but mordant peace plan by U.N. special envoy Kofi Annan, who has been trying for months to negotiate a solution to Syria’s crisis.

The Britain-based opposition Syrian Observatory for Human Rights said at least 62 people were killed across Syria in new violence on Saturday, including at least 14 government soldiers.

So far, it remains unknown why the government launched a large offensive against Tremseh. The Syrian government said the killings were carried out by armed gangs and terrorists, its shorthand for the anti-regime opposition. It said 50 people were killed before the army intervened and that three soldiers were killed.

But the U.N. has already implicated Assad’s forces in the assault. The head of the U.N. observer mission said Friday that monitors stationed near Tremseh saw the army using heavy weaponry and attack helicopters.

Anti-regime activists say government troops surrounded Tremseh early Thursday and shelled it before they pushed into the village alongside pro-regime militiamen from nearby communities and began killing people in the streets.

Assad’s forces have at times unleashed overwhelming and bloody firepower in assaults to overwhelm pockets of rebels who arise in pro-opposition areas. Syria’s uprising, which began in March 2011 with protests against Assad, has turned into an armed insurgency, with army defectors and locals who take up weapons forming rebel groups to fight the regime or defend their neighborhoods.

In the Tremseh fighting, it appeared that some fighters tried to resist after troops surrounded the village before dawn on Thurdsay, said Rami Abdul-Rahman, head of the Syrian Observatory for Human Rights, an opposition group based in London that monitors events through contacts on the ground. Later in the morning, the full assault on the town began, he said.

Online videos posted by activists showed a tank in the village, and dozens of bodies being buried in a mass grave. Another showed dozens of military vehicles, some with heavy machine guns, driving down a road that an off-camera narrator says is in Tremseh. Bystanders cheer and wave as they pass — presumably regime supporters from the neighboring villages. The videos could not be independently verified.

Abdul-Rahman said he has confirmed the names of 103 dead so far, all of them men. He said at least 50 were rebels. Among the dead were 30 whose bodies were completely burned and 18 who had been executed after their capture. Locals were reporting a toll as high as 200, he said, but added that he was still trying to confirm further deaths.

Activists said a state of shock reigned in Tremseh Saturday, while locals searched the area for remaining bodies and struggled to treat the hundreds of wounded.

“There are still martyrs under the rubble and in the fields,” said activist Bassel Darwish. One body was fished out of the Orontes on Saturday, he said, and many are thought to be scattered in nearby fields that residents can’t reach because of army checkpoints.

He said the overwhelming number of men killed was likely because the village’s women sought shelter during the assault while the men either tried to fight off the army or rescue the wounded.

Darwish said Syrian troops followed the observers into Tremseh on Saturday, causing residents to flee.

“The army entered so that no one would talk to the observers,” he said via Skype. “But everyone stayed away, afraid.”