IS seizes last Syria-Iraq crossing

According to international reports Islamic State militants have seized the last Syrian government-controlled border crossing between Syria and Iraq.

Government forces have reportedly withdrawn from al-Tanf - known as al-Waleed in Iraq - crossing as IS advanced, the Syrian Observatory for Human Rights (SOHR) said.

The loss of al-Tanf to IS follows the group's takeover of the ancient Syrian city of Palmyra on Thursday. The US says that fighting the militants will now be a "difficult challenge".

“IS now controls more than 95,000 square km of Syria, which is 50% of the country's entire territory,” the SOHR said.

Militants dominate the provinces of Deir al-Zour and Raqqa and have a strong presence in Hasakeh, Aleppo, Homs and Hama. However, correspondents say there are large areas under IS control in the east that are not very significant strategically.

Meanwhile, IS has also made significant gains in neighbouring Iraq, capturing the strategically-important city of Ramadi in Anbar province after weeks of fighting.

According to the BBC, the seizure of al-Tanf, in Syria's Homs province, enables IS to link up its positions in east-central Syria more directly with the ground they hold in Iraq's western Anbar province. Militants in Iraq are reported to be pressing eastwards from Ramadi down the Euphrates Valley towards Habbaniya where pro-government forces are massing for a proposed counter-attack on Ramadi.

The US has acknowledged the militants' gains are a "setback" for coalition forces targeting IS, but President Barack Obama insisted the US was "not losing" the war with the group.

"There's no doubt there was a tactical setback, although Ramadi had been vulnerable for a very long time," he told Atlantic magazine in an interview published on Thursday.

"The training of Iraqi security forces, the fortifications, the command-and-control systems are not happening fast enough in Anbar, in the Sunni parts of the country."

The United Nations have expressed concerns at reports that Syrian forces in Palmyra prevented civilians from leaving, ahead of its fall to Islamic State. It said it was "deeply concerned" about the plight of those remaining in the area, amid reports of executions.

IS has also overrun the World Heritage site adjacent to the modern city, raising concerns about its future given that IS has previously demolished ancient sites that pre-date Islam.