A Syrian was killed and another was wounded in a rare clash Wednesday between American troops and a group of government supporters who tried to block a U.S. convoy driving through a village in northeastern Syria, state media and activists reported.

The state-run media report said the man who was killed was a civilian, but the Syrian Observatory for Human Rights said it is not clear if he was a civilian or a member of a pro-government militia.

State media reports said the deceased man was among residents of a village east of the town of Qamishli who had gathered at an army checkpoint, pelting the U.S. convoy with stones and taking down a U.S. flag from one of the vehicles.

A video posted on state news agency SANA's website showed angry men firing small arms at a convoy of several armoured U.S. vehicles flying the U.S. flag. Some residents pelted the convoy with stones, while another dumped a bucket full of dirt on the back of one vehicle.

In one of the worst incidents of violence against U.S. troops deployed in northeastern Syria, a small fire appears to ignite on an armoured vehicle, apparently from fire bombs lobbed at the convoy. U.S. soldiers were seen standing in the middle of the melee, trying to disperse the crowd.

Other videos showed another vehicle stuck in the dirt, apparently having veered into a ditch, while another had a flat tire. In one video, a resident walked up to U.S. soldiers at one of the vehicles, holding a U.S. flag, screaming: "What do you want from our country? What is your business here?" A soldier tells the shouting man to "back off."

At that point, U.S. troops fired live ammunition and smoke bombs at the residents, the reports said.

A U.S. military spokesperson said coalition forces conducting a patrol near Qamishli encountered a checkpoint occupied by pro-Syrian government forces. After coalition troops issued a series of warnings in an attempt to de-escalate the situation, the patrol came under small-arms fire from unknown individuals, coalition spokesperson Myles Caggins said.

No Americans killed

"In self-defence, coalition troops returned fire. The situation was de-escalated and is under investigation," he added in a statement.

Air Force Lt.-Col. Carla Gleason, travelling with U.S. Defence Secretary Mark Esper in Brussels, said no Americans were killed in the incident.

Asked about the incident, Esper said in Brussels he was told there was an "altercation," without providing details.

"As far as I know today's incident did not involve the Russians," he said.

The clash marked a rare confrontation involving U.S. and Syrian troops in the crowded region where Russian forces are also deployed and was certain to escalate tensions.

Ninth year

Hundreds of U.S. troops are stationed in northeastern Syria, working with their local partners from the Kurdish-led Syrian Democratic Forces to fight against the Islamic State in Iraq and Syria (ISIS) group. The U.S. carries out patrols in northeastern Syria, but it was not immediately clear why the convoy drove into a government-controlled area.

The Syrian war, now in its ninth year, has pulled in international players including the U.S., Russia and Turkey.

With support from Russia, Syrian troops have been on the offensive for weeks in Idlib and parts of nearby Aleppo provinces, unleashing a humanitarian crisis with 700,000 people fleeing their homes and surging north toward the Turkish border.

At one point during the incident, U.S., Russian and Syrian flags could be seen next to each other, reflecting the complicated terrain in northeastern Syria. Some reports said a Russian convoy arrived on the scene to defuse the tension.

The Syrian Observatory for Human Rights said residents and armed pro-government militiamen in Khirbet Ammu blocked the path of a U.S. convoy. The militia fired in the air, prompting the American troops to fire smoke bombs. Tension escalated and U.S. troops killed one person, the Observatory said.

Erdogan vows to defend Turkey

The Observatory, which has a network of activists on the ground, said it is not clear if the killed was a civilian or a militia member. The Observatory also said that a Russian convoy arrived on the scene to defuse the tension.

In other violence in the country's northwest, Syrian President Bashar al-Assad's forces continued their advance in Idlib and Aleppo provinces near the border with Turkey. They took full control of a strategic highway that runs through the rebel-held territory and links the capital to northern Syria. The M5 highway had been under opposition control for most of the war.

Turkish President Recep Tayyip Erdogan addresses his ruling party members at parliament in Ankara on Wednesday. Erdogan said Wednesday that Turkey will attack government forces anywhere in Syria if Turkish troops are injured or killed. (Burhan Ozbilici/The Associated Press)

Russia's Defence Ministry said in a statement that Syrian troops fully cleared the M5.

"Syria's most important transport artery — the M5 highway linking the blocked northern capital of Aleppo with Hama, Homs and Damascus in the south — has been freed from terrorists," the statement said.

At least 13 Turkish soldiers have been killed by Syrian artillery fire this month as a result of the Idlib offensive.

Speaking in Ankara, Turkish President Recep Tayyip Erdogan said Wednesday that Turkey will attack Syrian government forces anywhere in Syria if another Turkish soldier is hurt.

Under a 2018 agreement with Russia in the Black Sea resort of Sochi, Turkey established a dozen military observation posts in Idlib, where it backs some opposition groups. Several of these posts have been surrounded by government forces in recent weeks.

Erdogan said he had spoken to Russian President Vladimir Putin by telephone about the situation in Idlib.

The Kremlin said that the phone conversation underlined the need to fully implement the Russian-Turkish agreements.

Putin's spokesperson Dmitry Peskov added that despite a pledge by Turkey, militants in Idlib have continued to launch attacks on Syrian troops and threaten Russian facilities in Syria. "It's inadmissible and it runs contrary to the Sochi agreements," Peskov said in a conference call with reporters.