A suicide attack by Islamic State (IS) militants has brought fierce fighting back to the Kurdish town of Kobane in northern Syria.

Dozens of civilians are believed to have been injured in the attack, after IS militants drove a vehicle packed with explosives, known as a VBIED (vehicle-borne improvised explosive device), over the border from Turkey and detonated it near the Morshed Binar border gate shortly after midnight local time (21:00 GMT Wednesday).

Syrian Observatory for Human Rights director Rami Abdel Rahman said that the battle is still raging in the centre of the strategically important town.

The attack raises questions about how dozens of IS fighters and a VBIED were able to travel within Turkey and cross the border without being stopped by the Turkish intelligence or military personnel that closely monitor the area.

Turkey has long been accused of turning a blind eye to IS militants within its borders, and its inability to properly secure its border will add further strain to its relationship both with the Kurdish people and their allies in the West.

The IS assault on Kobane in October 2014 brought worldwide attention to the plight of the Kurds in Syria. Kurdish YPG fighters were able to repel the attack with the help of a US-led bombing campaign in a fierce three-month battle. Since then, YPG fighters and their Free Syrian Army (FSA) allies have made strong gains against IS, winning back a large swathe of territory from Kobane on the Turkish border in an 40km arc to the banks of the Euphrates, Qertel to the east, and Mamid to the south.

Kurdish forces have been closing in on the de-facto IS capital of Raqqa in recent weeks, with YPG fighters now just 50km from the city. It is this threat that likely led IS to launch an assault on Kobane.