Kurdish fighters seized a key town in northern Syria from ISIS on Monday, cutting a supply lifeline from the jihadists' de facto Syrian capital, a monitor said.
"The Kurdish People's Protection Units (YPG) took full control of Sarrin on Monday after three weeks of intense clashes," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
Sarrin lies along the M4 highway, which ISIS uses to transport fighters and supplies between Aleppo province and the group's de facto Syrian capital of Raqqa in the east, Abdel Rahman said.
The town's capture cuts off ISIS's main access route to parts of Aleppo province, where the jihadists are fighting both Kurdish forces and rebel groups.
"Sarrin was also used as a base for IS to attack the Kurds in Aleppo province, so those attacks will probably decrease as well," he told AFP using an alternative acronym for the so-called "Islamic State" group.
Mustafa Ebdi, a Kurdish activist from the flashpoint town of Kobane some 40 kilometers (25 miles) north of Sarrin, said the YPG were still combing through the town to clear it of potential ISIS suicide bombers.
YPG forces began their offensive on Sarrin on July 6 with air support from the US-led coalition fighting ISIS in Syria and Iraq.
The capture of the town, which lies on the east bank of the Euphrates river, is the latest victory for Kurdish forces in Syria against ISIS.
They defeated IS forces in Kobane in January, expelling them with the help of coalition air strikes.
And on June 16, they pushed ISIS out of Tal Abyad, a town on the Syrian-Turkish border used by ISIS to bring in weapons and fighters to Raqqa.
The Syrian conflict began with anti-government protests in March 2011, but has developed into a multi-front civil war involving Kurds and jihadists of both ISIS and Al Qaeda, as well as other rebels and regime loyalists.
Kurdish advances come on the same day as Kurdish fighters in Syria say their positions were bombarded by the Turkish army.
The Turkish military denied targeting Syrian Kurds after Kurdish forces and a monitoring group said tanks shelled Kurdish-held villages in northern Syria, a Turkish government official said on Monday.
"The ongoing military operation seeks to neutralise imminent threats to Turkey's national security and continues to target ISIS in Syria and the PKK in Iraq," the official told AFP, referring to the Islamic State and the outlawed Kurdistan Workers' Party, which is linked to the YPG and its political branch, the PYD.
He said the Syrian Kurdish "PYD, along with others, remains outside the scope of the current military effort."
In a statement, the YPG said Turkish tanks hit its positions and those of allied Arab rebels in the village of Zur Maghar in Aleppo province.
The "heavy tank fire" wounded four members of the allied rebel force and several villagers, the YPG said.
It said there was a second, later round of shelling against Zur Maghar and another village in the same area.
The Turkish official, speaking on condition of anonymity, also said: "We are investigating claims that the Turkish military engaged positions held by forces other than ISIS."
Turkey has launched a two-pronged "anti-terror" cross-border offensive against jihadists and the PKK militants after a wave of violence in the country, pounding their positions with air strikes and artillery.
Early on Monday, Turkish police detained 15 people with suspected links to ISIS in the Hacibayram district of the capital Ankara, the state-run news Anatolia news agency reported.
Eleven of the 15 detainees were foreigners, Anatolia said, adding that the operation was backed by around 500 police officers who raided several addresses.
The Turkish official told AFP the operations against ISIS and PKK were continuing, adding that a total of 900 people had been detained so far with links to ISIS, PKK and other leftist organisations.
"We are fighting against all terrorist organisations," said the official.