Despite daily bombing raids by coalition warplanes, the Islamic State (IS) group has captured nearly half of the Syrian border town of Kobane and seized most of Iraq's largest province, Anbar.

The progress of the IS jihadists is set to dominate the meeting in Washington of military chiefs from the 22 countries in the US-led coalition.

Top brass, including national chiefs of staff, will also meet US President Barack Obama at Andrews Air Force Base outside the US capital, the White House said.

The generals will "discuss a common vision on the counter-ISIL (-IS) campaign, challenges and the way ahead," said US Colonel Ed Thomas, spokesman for the chairman of Joint Chiefs of Staff.

Australia, Bahrain, Belgium, Britain, Canada, Denmark, Egypt, France, Germany, Iraq, Italy, Jordan, Kuwait, Lebanon, the Netherlands, New Zealand, Qatar, Saudi Arabia, Spain, Turkey, the United Arab Emirates and the United States will all be represented.

It is the first time such high-ranking military officials from so many nations have come together since the coalition -- which, on paper, now includes about 60 countries -- was formed in September.

Turkey's call for the establishment of a protective buffer zone along its border with Syria, where the jihadists have pushed into the heart of the predominantly Kurdish town of Kobane, is also expected to be on the agenda.

Ankara, which has faced a three-decade Kurdish insurgency, has tightened security of its porous Syrian border after the escalating fighting in Kobane sparked the exodus of 200,000 refugees.

Turkish jets late Monday bombed targets in the southeast of the country where members of the Kurdistan Workers' Party are based, the first strikes on the outlawed group since a 2013 ceasefire, a security source said.

French President Francois Hollande on Tuesday urged Turkey to open its frontier with Syria to help Kurdish fighters in Kobane, warning that the town "could at any moment fall into the hands of the terrorists".

He also called on "all countries concerned", including those not in the coalition fighting IS, to provide weapons to those battling the jihadists, notably in Kobane.

- Death toll mounts -

A Kobane politician who is now a refugee said IS fighters had surrounded the town to the south, east and west, and warned of a "massacre" if they take the northern front bordering Turkey.

Fighting spread to less than a kilometre (half a mile) from the barbed wire frontier fence, with the jihadists carrying out three suicide car bombings in the border zone, the Syrian Observatory for Human Rights said.

The Britain-based monitoring group later said IS had advanced into central Kobane, seizing a major building and squeezing the Kurdish defenders into its northern half bordering Turkey.

The Kurdish fighters, meanwhile, recaptured the strategic hilltop of Tel Shair west of Kobane on Monday, according to the Observatory, which said it had changed hands several times.

Hundreds of people have been killed in the battle for Kobane, mostly fighters from both sides.

On Monday at least nine IS jihadists were killed, including the three suicide bombers, as well as six Kurdish fighters, the Observatory said.

Fighting continued on Tuesday in the northern outskirts near the border, according to an AFP reporter on the Turkish side of the frontier.

Witnesses reported several air strikes on Kobane during the night and into Tuesday morning.

With the jihadists advancing on its doorstep, NATO member Turkey has come under intense pressure to take action as part of the US-led coalition.

Pentagon chief Chuck Hagel told reporters in Peru that he was "optimistic about progress" in talks with Turkey about a possible role in the fight against IS.

- Anbar teeters -

Concern has also been growing over Iraq, where IS fighters have been threatening to seize more territory.

Iraqi forces are reported to be under intensifying pressure in Anbar province, a vast region stretching from near Baghdad to the border with Syria.

On Monday, security sources said Iraqi troops stationed on the edge of Heet in Anbar had withdrawn to another base, leaving the city under full jihadist control.

Pro-government forces have also been in trouble south of IS-held Mosul around the Baiji oil refinery, where US aircraft on Sunday for the first time dropped supplies including food, water and ammunition to Iraqi troops.

IS is accused of committing widespread atrocities in areas it controls, including attacks on civilians, mass executions, beheadings and enslaving women.

Meanwhile, rights watchdog Amnesty International accused Shiite militias backed by the Iraqi army of committing war crimes against civilians in their fightback against IS.

burs/dr/srm