BEIRUT: ISIS jihadis battling for control of the Syrian town of Ain al-Arab suffered some of their heaviest losses yet in 24 hours of clashes and U.S.-led airstrikes, activists said Sunday.

At least 50 jihadis were killed in the embattled border town in suicide bombings, clashes with Kurdish defenders and airstrikes, the Syrian Observatory for Human Rights said.

The Britain-based Observatory also said the U.S.-led coalition battling ISIS hit at least 30 targets in and around Raqqa, the jihadis’ de facto capital.

There were no immediate details of a toll in the Raqqa strikes.

Syrian regime strikes Sunday killed at least 29 civilians, among them seven women and three children, the group said.

The deaths in Ain al-Arab, known widely by its Kurdish name Kobani, came Saturday after ISIS militants launched an unprecedented attack against the border crossing separating the Syrian Kurdish town from Turkey.

Kurdish officials and the Observatory alleged the attack was launched from Turkish soil, a claim the Turkish army dismissed as “lies.”

Turkey’s main pro-Kurdish party pressed Prime Minister Ahmet Davutoglu over whether a probe had been launched into claims that an attack by jihadis on a border post had been launched from Turkish soil.

“Has any investigation been launched yet into the allegations that an explosive-laden car, said to be coming from Turkey, exploded as it crossed into Kobani from the Mursitpinar border post?” People’s Democratic Party lawmaker Faysal Sariyildiz said in a written parliamentary question to Davutoglu.

ISIS began advancing on Ain al-Arab on Sept. 16, hoping to quickly seize the small frontier town and secure its grip on a large stretch of the Syrian-Turkish border, following advances in Iraq.

At one point it looked set to overrun the town, but Kurdish Syrian fighters, backed by coalition airstrikes and an influx of Iraqi Kurdish peshmerga forces, have held ISIS back.

In Raqqa province, the coalition carried out strikes against at least 30 ISIS targets on the northern outskirts of Raqqa city and struck Division 17, a Syrian army base which jihadis captured earlier this year.

“We can’t say it’s the largest set of raids they have carried out, but it’s been a long time since we’ve seen this number of targets hit,” Observatory chief Rami Abdel-Rahman said.

The coalition began carrying out airstrikes against ISIS on Sept. 23, and stepped up raids in Ain al-Arab in a bid to prevent the city falling to the jihadis.

The U.S. coordinator of the coalition said earlier this week that at least 600 ISIS fighters had been killed in airstrikes and that the group had made easy targets of its fighters by pouring them into Ain al-Arab.

But Syria’s Foreign Minister Walid al-Moallem said the airstrikes were having little effect and that unless Turkey closed its border to jihadis, the group would be unharmed by the attacks.

Damascus has regularly accused Turkey of supporting “terrorism” because of its support for the opposition. Turkey denies the charges.

Erdogan is to receive Russian President Vladimir Putin, whose country is a key ally of Syria, in Ankara Monday for talks about the conflict, which has killed nearly 200,000 people since March 2011.

In Syria, the regime kept up its deadly airstrikes, including raids that killed 21 civilians including seven women and two children in the town of Jassem in southern Deraa province Sunday.

Regime strikes in Anadan village in the northern province of Aleppo killed eight civilians including a child, the Observatory said.