A US-led coalition intensified airstrikes against "Islamic State" (IS) militants on Thursday in the Syrian city of Kobani, which lies on the Turkish border.

Despite the bombardment, it is believed that over one third of the city is now controlled by the militant Islamic radicals.

The US approved airstrikes against key IS positions in Iraq in September. However, targeting the insurgents - who seek to set up a caliphate in most of the Middle East - in Syria is more complicated, as the coalition does not wish to strengthen Syrian President Bashar al-Assad, who is accused of carrying out crimes against humanity, including using chemical weapons against civilians, during the ongoing Syrian civil war, which began in March 2011.

Kobani a 'tragedy'

Speaking to reporters in Boston on Thursday, US Secretary of State John Kerry said, "Kobani is a tragedy because it represents the evil of ISIS but it is not the definition either of the strategy or the full measure of what is happening with response to ISIS," Kerry said, referring to a former name for the IS terrorist group.

He added it was likely that other towns were vulnerable to the threat posed by the insurgents and that coalition efforts would take "weeks and months" to play out, Reuters news agency reported.

"The primary goal of this effort has been to provide the space for Iraq to be able to get its government in place and to begin to push back and to begin to be able to deprive them (Islamic State militants) of their command and control, their supply centers and their training. That is taking place."

Increased pressure on Turkey

Supporters of US-led airstrikes against the IS in Syria and Iraq have grown annoyed with Turkey, whose president, Recep Tayyip Erdogan, has refrained from providing military support to the mission. However, the ongoing battle for Kobani poses an imminent threat to Turkish security, a problem that officials from the United States and European Union hope will help prompt Ankara to join the internationally coordinated mission.

Turkish Foreign Minister Mevlut Cavusoglu and newly appointed NATO Secretary-General Jens Stoltenberg kicked off a series of consultations between NATO, the US and Turkey with a press conference to address the issue in Ankara on Thursday.

Cavusoglu emphasized that Turkey had not changed its stance on key issues, namely the necessity of sending in troops to Syria.

"There is a necessity [for] political change. As long as [Syrian President Bashar al-Assad] is in power, this status quo will continue. We now have different groups in the area and we can never guess where the terrorist groups will target and will continue to fight," the Turkish foreign minister said, adding: "[You] can't challenge the balance of power with air bombardments."

"It is not realistic to expect Turkey to conduct a ground operation on its own," he added.

Turkey has demanded the implementation of a no-fly and buffer zone to absorb the nearly 200,000 Syrian refugees who have already fled fighting in Kobani alone.

Though France has supported the idea, Washington has expressed reluctance, given the cost and complexity of creating such a zone.

NATO chief Stoltenberg said at Thursday's press conference, however, that a no-fly zone "has not been on the table of any NATO discussions yet and it is not an issue which is discussed in NATO."

Kurdish protests

For four consecutive days, demonstrations against the IS advance in Syria have taken place in a number of different cities across Germany, including Hamburg, Celle, Dortmund and Munich.

Protests turned violent late on Wednesday as Kurdish demonstrators clashed with Islamists in Hamburg. Dozens of people were arrested, many of whom were released in the early hours of Thursday.

A police spokesman said those arrested were of Turkish, Syrian and German nationalities and that they were between the ages of 18 and 38.

Thousands of Kurds have also taken to the streets in Turkey to demand President Erdogan approve military action against IS across the border. Dozens have been killed in clashes between protesters and security forces since Tuesday and curfews have been imposed in five provinces.

sb, tj (Reuters, AP)