The Syrian government has warned of retaliation if the US strikes again across the border from Iraq, demanding that its sovereignty be respected.
The warning came a day after Syria said eight people were killed in a US helicopter attack in the border village of Sukariya on Sunday.
On Monday Syria's foreign minister accused the US of conducting a planned act of "criminal and terrorist aggression" in broad daylight with "blunt determination".
Walid Muallem, speaking in London, said he did not believe the killing of civilians had been a mistake and warned that "we would defend our territories" if there is a repeat of the weekend raid.
"All of them are civilian, unarmed, and they are on Syrian territory," he said.
Muallem said that among the dead were a farmer, three children and a fisherman.
"Killing civilians in international law means a terrorist aggression. We consider this a criminal and terrorist action," he said.
Syrian state television reported that four US military helicopters were involved in the incident as families buried the dead in the village near the town of Abu Kamal.
The area targeted lies close to the Iraqi border city of Qaim, which in the past has been a crossing point for fighters, weapons and money used to fuel the armed Sunni opposition against Iraq's government.
"American soldiers ... attacked a civilian building under construction and fired at workmen inside, causing eight deaths," the television report said.
Muallem said his government held the US responsible for the civilian deaths and wanted an investigation to explain why the raid had been carried out.
He also raised questions about the impact of a pact between the US and Iraq over troop deployment next year on neighbouring countries.
Following news of Sunday's attack, the Syrian government summoned the senior US and Iraqi envoys to Damascus to protest against the raid, the Syrian Arab Sana news agency said.
The US has not officially responded to Syria's accusations but an unnamed government source was quoted as saying that the target of the US raid was a smuggling ring taking foreign fighters into Iraq.
The unnamed official said Abu Ghadiya, a former lieutenant to Abu Musab al-Zarqawi, the late leader of al-Qaeda in Iraq, had been killed in the raid.
"It was a successful operation ... He [Abu Ghadiya] is believed to be dead," the official said.
"He had knowledge of many of the so-called 'rat lines' or smuggling routes [into Iraq] ... This undoubtedly will have a debilitating effect on this foreign fighter smuggling network."
Abu Ghadiya, also known as Badran Turki Hishan Al-Mazidih, was among those killed, a US counterterror official confirmed on Monday.
The attack was carried out at 4:45pm local time.
A ground attack was chosen over a missile strike to reduce the chances of hurting civilians not associated with Abu Ghadiya's network, the official said.
The US official confirmed that women and children were at the house.
He did not specifically address whether any women and children were among the casualties. He said "several" males were killed and identified them as Abu Ghadiya's bodyguards.
The US operation was precipitated by intelligence that Abu Ghadiya was planning an imminent attack in Iraq, another senior US official told The Associated Press news agency.
|Syria says that civilians were the only victims of the alleged raid [AFP]
US intelligence picked up similar reports last spring.
That information, not sufficiently detailed to act on, was followed by the murder of 11 Iraqi policemen just across the border from Abu Ghadiya's Syrian compound, the official said.
Abu-Ghadiya personally led the attack, the official said.
Earlier Hoda Abdel Hamid, Al Jazeera's correspondent in the northern Iraqi city of Irbil, said the purported US raid seemed to be in contradiction to comments by US officials that Syria had improved its border security.
The Americans had actually praised the role of Syria over the last year, which made the alleged raid puzzling, our correspondent said.
Muallem, who was in London for talks with his British counterpart, said US officials knew "full well that we stand against al-Qaeda".
"They know full well we are trying to tighten our border with Iraq," he said.
Speaking to Al Jazeera on Tuesday, Theodore Karasik, director of research at the Dubai-based Institute for Near East and Gulf Military Affairs, said: "This is a traditional, tribal, transnational network area - there are goods and services moving between Syria and Iraq in this location. Unfortunately, Syrian territory is used by al-Qaeda supporters to transit between Syria and Iraq, and I assume that there was actionable intelligence that someone of significant interest was there, and he was therefore targeted."