Rebel fighters trying to oust President Bashar Assad shot down a fighter jet as it flew over the northern Syrian town of Atarib in Idlib province, a witness said.

The witness, an independent journalist who asked to remain anonymous, said rebel fighters were attacking a military base near the town when the jet flew over and rebels shot it down with anti-aircraft guns.

Vastly outgunned, rebels say they need surface-to-air missiles to take down planes and helicopters used by the Syrian military to bombard opposition strongholds.

Fighters use outdated anti-aircraft machine guns that are welded to pickup trucks but they are inaccurate and useless if the military aircraft fly above a certain altitude.

On August 27 fighters shot down a helicopter on the outskirts of Damascus and three days later rebels said they had brought down a jet in Idlib, near the Turkish border.

Activists say more than 27,000 people, mostly civilians, have been killed in the 18-month-old revolt in Syria, which began with peaceful street protests that provoked a military crackdown and mushroomed into civil war.

Despite calling for Assad to step down, the West is wary of arming disparate rebel groups.

Violence across the country

Syrian government troops and rebels clashed on Saturday near a border crossing with Jordan, according to opposition activists, as reports of violence across Syria continued.

The fighting, accompanied by heavy shelling from government troops, raged near the busy Al-Nasib border crossing located on a highway linking the Syrian and Jordanian capitals, according to the activists.

Elsewhere in Syria, activists said government jets bombarded areas in Yabroud, near the capital Damascus, and pro-rebel districts in the embattled northern city of Aleppo.

Independent verification of reports out of Syria is constrained by media restrictions imposed by the government in Damascus.

At least 150 people, mainly near Damascus and Aleppo, were killed across Syria on Friday, reported the opposition Syrian Observatory for Human Rights.

Iraq has barred a North Korean plane from using its airspace on suspicion it was carrying weapons for Syria, regional media reported. Earlier this week, U.S. officials accused Iraq of allowing Iran to fly arms to Syria using the Iraqi airspace, a charge denied by Baghdad.North Korea and Iran are allies of Syrian President Bashar Assad.