Iraq's Government expressed outrage at the relocation, which would have enabled the 300 Islamic State fighters on board the convoy to reinforce militant positions in Iraq. The US military vowed to prevent them from doing so and on Thursday blocked the convoy's path, by bombing the desert road ahead of it.
At least some of the buses have since been stranded in the desert between Syrian Government and Isis lines, with US warplanes circling overhead to deter any further attempts to reach Isis territory.
Today, Iran's Foreign Ministry slammed the US military's surveillance of the buses as "illogical" and said the lives of pregnant women are at risk, according to the official Islamic Republic News Agency.
The US military said six of the buses had crossed back into government-held territory and headed towards the Syrian Government-controlled town of Palmyra, leaving 11 buses stuck in the desert. The whereabouts of the six buses that headed to Palmyra were not clear.
Hizbollah said that four of the buses reached territory controlled by Isis, in fulfillment of the Hizbollah deal, and that six were stuck in the desert. It did not say what had happened to the other seven buses.
According to Syrians in the area and Iraqi officials, however, all or most of the original fighters who set out on the convoy had got off the buses and made their way to Iraq, using back roads to bypass the path bombed by US warplanes.
Omar Abu Layla, who heads an activist network called Deir al-Zour 24, said the fighters travelled on foot to meet up with Isis fighters nearby and have been transported to two western Iraqi towns, Rawa and Aana. He cited the accounts of two reporters in his network who live in the area.
Two Iraqi officials said they believed all of the fighters and their families had arrived in Rawa in recent days. Residents told Mohammed Karbouli, a member of Iraq's parliamentary committee on defence and security, that hundreds of Isis fighters from Syria showed up in Rawa at the weekend and that they were apparently those from the convoy.
"That deal was a big mistake, and it harms only Iraq," he said.
Asmaa Al-Ani, a member of the local council in Anbar province, said residents of Rawa told her that about 700 Isis fighters and their families had arrived and had taken up residence in empty homes. "These reinforcements will have a negative impact on the military situation for the coming operations," she said, referring to the Iraqi Army's plans to recapture the area, one of the last remaining pockets in Iraq controlled by Isis.
The claims left it unclear who, if anyone, may still be aboard the buses stranded in the desert. Hizbollah has accused the US military of endangering the lives of women and children who are on the buses, but the US military says it will not prevent supplies from reaching the vehicles.