Turkish President Recep Tayyip Erdogan on Thursday dismissed as “propaganda” accusations that Islamic State (ISIS) fighters had been allowed to cross from Turkey into Syria to launch a fresh assault on the symbolic battleground town of Kobane.

“We condemn the heinous attack by the terrorist IS organization that targeted innocent civilians in the city of Kobane,” Erdogan said in a speech, according to the AFP news agency.

Dozens of civilians and fighters on both sides were killed when the ISIS jihadists made a surprise return to Kobane on Thursday, detonating a suicide car bomb near the border and battling Kurdish fighters in the city. Two more bombs exploded later in the day.

Claims circulating on the Internet suggested several cars loaded with ISIS jihadists had passed through the Mursitpinar border crossing in Turkey to make their way into Kobane.

Describing those allegations as “defamation and propaganda”, Erdogan said, “No one has the right to link Turkey to terrorist organizations”.

Erdogan’s comments came hours after Turkey’s Deputy Prime Minister similarly rejected the allegations, calling them “a lie and part of a black propaganda”.

The Syrian Observatory for Human Rights said at least 35 civilians and Kurdish fighters were killed in the car bomb and subsequent fighting in the center and south of the town, along with 22 ISIS terrorists.

Turkish officials, meanwhile, said four victims had died in Turkish hospitals while 135 wounded received treatment on the Turkish side of the border.

The Turkish government said video footage taken from Turkish border security units and broadcast by the state-run Anatolia news agency showed a bomb-laden car did not pass through the Turkish border crossing.

Nevertheless, Kurdish activists accused Turkey on social media of assisting ISIS, with the hashtag #TerroristTurkey becoming a trending topic on Twitter.

The accusations come amid growing tensions between Syrian Kurds and Turkey.

Turkey says Syrian Kurdish forces who recently made gains in Syria against IS are linked to the Kurdistan Workers’ Party (PKK), which for decades has waged a deadly insurgency inside Turkey.

Western states have repeatedly accused Turkey of not doing enough to halt the flow of jihadists in both directions across its border with Syria.

Turkey fiercely rejects the accusations, saying it is making every effort to secure a long border and in turn has accused the West of not playing its part to shoulder the burden of hosting refugees from Syria.

AFP contributed to this report.