At least 21 people have been killed in Turkey when protests against Islamic State militants turned violent.

Kurdish people living in Istanbul and Ankara, clashed with police, as the fallout from the war on the extremists spreads into Turkey.

The US President Barack Obama says a growing international coalition is determined to confront the extremists.

The demonstrations called by the main pro-Kurdish party, the People's Democratic Party (HDP), stem from claims that Ankara is failing to intervene militarily against IS jihadists fighting for the Syrian border town of Kobani.

Fresh coalition airstrikes have targeted fighters around the town, where some 400 people are believed to have been killed and thousands displaced during weeks of fighting.

However, airstrikes alone may not be able to stop the advance of Islamic State fighters in Syria, US officials have warned.

Barack Obama met military commanders to discuss the campaign against IS in Syria and Iraq amid fears troops would be needed on the ground.

"Our strikes continue, alongside our partners. It remains a difficult mission," the US President said. "As I've indicated from the start, this is not something that is going to be solved overnight."

Pentagon spokesman Rear Admiral John Kirby said: "Airstrikes alone are not going to do this, not going to fix this, not going to save the town of Kobani.

"We know that. And we've been saying that over and over again. We all need to prepare ourselves for the reality that other towns and villages and perhaps Kobani will be taken by IS."