Islamic State crisis: Heavy fighting on Iraq-Syria border
Heavy fighting has been reported across a key border crossing between Iraq and Syria, where Kurdish forces are battling Islamic State militants.
Iraqi Kurdish troops are said to have recaptured the town of Rabia, but suffered heavy casualties.
Meanwhile, IS fighters have been trying to dislodge Syrian Kurdish forces on the other side of the border.
It comes amid continuing air strikes by a US-led coalition on IS targets both in Syria and Iraq.
Information from Kurdish sources suggests Tuesday's strikes by two British Tornado jets helped the Kurds retake an "important border crossing" at Rabia, says the BBC's Clive Myrie in Irbil, northern Iraq.
These were the first British raids on IS targets.
In other developments:
- In Syria, US warplanes carried out 11 air strikes over the last two days, targeting IS positions near Deir al-Zour, Sinjar, Mazra al-Duwud and Aleppo, destroying a number of armed vehicles, artillery pieces and one tank
- In Iraq, 11 US raids on Tuesday in the north-west, and near the Mosul Dam and Baghdad destroyed IS armoured and transport vehicles and a checkpoint
- At least 20 people were killed in bomb attacks on Shia areas of the Iraqi capital Baghdad; deaths were also reported in similar attacks in the holy Shia city of Karbala
- UN humanitarian chief Valerie Amos said 11 million people inside Syria needed urgent aid, warning that without extra funding the "World Food Programme will be forced to end its operations completely within two months".
In a separate development, Turkish tanks have taken up positions along the border near the Syrian town of Kobane after several shells hit Turkish territory during clashes between IS and Kurdish fighters.
The Turkish government asked parliament to authorise military action against IS in Iraq and Syria, and MPs are expected to discuss the issue on Thursday.
Senior Iraqi Kurdish officials said their Peshmerga special forces had made good initial progress during their dawn offensive in Rabia.
The officials said that by nightfall, Rabia was firmly in Kurdish hands, although IS militants continued to hold out in just one building.
Rabia lies about 100km (60 miles) north-west of Mosul - the biggest city controlled by IS.
But the Iraqi Kurdish forces also took heavy casualties - including the loss of a senior commander - when three suicide car bombers blew themselves up among the Kurdish troops.
The bombers are believed to have travelled from IS-controlled areas further east.
The BBC's Jim Muir, in Irbil, says control of the Rabia crossing and cutting IS supply lines are seen as important steps towards an eventual move to regain the town of Sinjar and its nearby mountain.
Militants overran that area in August forcing tens of thousands of civilians from the minority Yazidi community to flee for their lives.
The other side of the border is controlled by Syrian Kurdish fighters, who themselves have been coming under attacks from IS.
More than 30 Syrian Kurdish fighters are reported to have been killed as the jihadists took over several villages south of the border crossing.
However, the crossing itself is said to be still under Kurdish control.
IS has recently seized large swathes of territory both Iraq and Syria.
- Formed out of al-Qaeda in Iraq (AQI) in 2013, IS first captured Raqqa in eastern Syria
- It captured broad swathes of Iraq in June, including Mosul, and declared a "caliphate" in areas it controls in Syria and Iraq
- Pursuing an extreme form of Sunni Islam, IS has persecuted non-Muslims such as Yazidis and Christians, as well as Shia Muslims, whom it regards as heretics
- Known for its brutal tactics, including beheadings of soldiers, Western journalists and aid workers
- The CIA says the group could have as many as 31,000 fighters in Iraq and Syria