(AP) BEIRUT — Dozens of Islamic State group members and their families have crossed into areas controlled by the extremists despite US threats to bomb the convoy days after they left the Lebanon-Syria border, Syrian opposition activists said Saturday.

The opposition activists’ announcement came after the US-led coalition fighting IS said the 17-bus convoy of IS militants and their families that left the Lebanon-Syria border six days ago is still stranded in the Syrian desert.

More than 300 militants and their families are in the convoy after vacating the border area as part of a Hezbollah-negotiated deal to transport them to an IS-held town in eastern Syria near the Iraqi border.

Hezbollah said in a statement Saturday that warplanes of the US-led coalition are still preventing the convoy from moving east and barring anyone on the government side from reaching them, warning that the wounded and elderly people could die.

Hezbollah said that six buses are still in areas controlled by the Syrian government and warned that if they are hit civilians will be killed. It added that if aid does not reach the convoy because of the aerial imposed siege, “only the Americans will bear the responsibility” for what happens.

“The so-called international community and international institutions should intervene to prevent the occurrence of an ugly massacre,” the Lebanese group said.

The US-led coalition issued a statement Friday saying it has sought an unspecified solution that would save the women and children in the convoy from further suffering.

Earlier this week, an airstrike by the US-led coalition created a crater in a road that the buses had intended to take and destroyed a small bridge to prevent the convoy from moving further east.

Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, said dozens of fighters and civilians left the buses and drove into IS-held parts of the eastern province of Deir el-Zour in 12 civilian vehicles.

Opposition activist Omar Abu Laila, who is from Deir el-Zour and currently lives in Europe, gave an account similar to that of Abdurrahman adding that most of them have crossed over. Abu Laila is with DeirEzzor 24, an activist group that has reporters throughout the eastern province.

Regime forces make gains

Meanwhile, in central Syria, government forces captured wide areas from IS under the cover of Russian airstrikes forcing hundreds of people to flee to government-controlled areas as well as areas run by insurgent groups.

The Russian Defense Ministry said Saturday that Syrian forces backed by Russian warplanes have “liberated” the town of Aqeirbat, defeating a large IS contingent.

“The last major center of resistance of terrorists in the central part of Syria has been eliminated,” the ministry said in a statement cited by state news agency TASS.

The Observatory said the fighting made some 750 people, many of them women and children, flee to areas controlled by the al-Qaeda-linked Levant Liberation Committee, a main rival of IS. It said thousands more are waiting for a safe corridor in order to flee areas controlled by IS.