"Syria draws attention to this aggressive act and expects the UN Security Council and member countries to assume their responsibility by preventing a repetition of this dangerous violation," the letter read.
It called for the Security Council "to hold the aggressor responsible for the deaths of the innocent Syrian nationals".
The letter comes two days after Syria said eight people had been killed in a US helicopter attack in the border village of Sukariya.
The Syrian government has ordered the closure of a US school and cultural centre in the capital, Damascus, in the wake of the raid.
The Damascus Community School, also known as the American School, was told to close its doors on Tuesday.
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.
An unnamed US official said that a lieutenant to the late leader of al-Qaeda in Iraq had been killed in the raid, but the US is yet to say officially whether or not it carried out the attack.
'Children dead'
Muallem said that a farmer, three children and a fisherman were among the dead.
"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 had been involved in the incident near the town of Abu Kamal.
The area is 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 US-backed 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.
Diplomat summoned
Following news of Sunday's attack, the Syrian government summoned the senior US and Iraqi envoys to Damascus, the Syrian capital, to protest against the raid, Syrian media reported.
An unnamed US government source was quoted as saying that the target of the raid was a smuggling ring taking fighters into Iraq.
The official said Abu Ghadiya, a former lieutenant to Abu Musab al-Zarqawi, the late leader of al-Qaeda in Iraq, had been killed.
"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 said on Monday.
The official said a ground attack was chosen over a missile strike to reduce the chances of hurting civilians, and confirmed that women and children had been at the house.
He did not address whether any women and children were among the casualties. He said "several" males had been killed and identified them as Abu Ghadiya's bodyguards.
Puzzling turn
The US operation was precipitated by intelligence that Abu Ghadiya was planning an 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 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 past year, which made the alleged raid puzzling, our correspondent said.
Muallem, who had been 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."