BEIRUT (Reuters) - A U.S.-backed militia alliance in Syria denied reports on Monday of an attack on one of its vehicles near a base housing U.S.-led international troops.

A local security source said a blast had hit a vehicle belonging to the U.S.-backed Syrian Democratic Forces (SDF) alliance, without harming anybody. The Syrian Observatory for Human Rights, a war monitor, said one person had been killed when a bomb hit a vehicle near a base housing U.S.-led international troops outside Ain Issa in northern Syria.

However, an SDF spokesman denied that any of its groups were subject to any attack in that area in the past two days.

The U.S.-led international coalition also said none of its troops were present or affected by any recent explosions near Ain Issa.

The United States is believed to have about 2,000 troops on the ground in Syria, with France and Britain also having contributed ground forces to its coalition.

With air and special forces backing from the coalition, the SDF has captured almost all of the quarter of Syria east of the Euphrates since beginning a campaign against Islamic State fighters that controlled the area in 2015. It is now the largest territory in Syria outside government control.

The Observatory also reported on Monday that the SDF had made wide advances against Islamic State in one of the last desert areas the militant group controls near the border with Iraq. Islamic State holds only a few remote pockets of ground in eastern Syria after offensives by both the U.S.-backed SDF and the Syrian army backed by Iran and Russia.