Islamic State tightens siege of Syria border town Kobane
Islamic State militants are advancing on the Syrian town of Kobane, where they are battling Kurdish fighters.
The clashes are visible from Turkey, where some protesters have stormed a border fence to go to defend the town.
Earlier, the US said it had destroyed four tanks and damaged another during a fourth night of bombardments in Syria.
The UK parliament has voted to conduct air strikes against IS in Iraq, while Belgium and Denmark have also announced they will take part in the operation.
IS controls much of north-eastern Syria and earlier this year seized swathes of territory in neighbouring Iraq, including the second city, Mosul.
Some European leaders are wary of bombing Syria, as the government there has not asked for foreign assistance against IS, unlike Iraq.
IS fighters have besieged Kobane, leading some 140,000 people to flee into Turkey over the past week.
However, some on Friday tried to return to help stem the militants' advance and Turkish forces fired tear gas and water cannon to stop them.
During the fighting for Kobane, at least two shells landed on Turkish territory, witnesses said.
One man watching the battle from the Turkish side of the border asked why air strikes were not being conducted to defend the town, which has a population of some 400,000.
"Where is America, where is England, why are people not helping?" a villager called Ali told Reuters news agency.
Speaking at the Pentagon on Friday, US armed forces chief Gen Martin Dempsey said the air campaign had damaged Islamic State but would not be enough to defeat it.
He said a political solution and a ground campaign would both be needed in Iraq and Syria.
Gen Dempsey said that a force of up to 15,000 fighters - to be drawn from Syria's moderate opposition - would be needed on the ground in Syria. He said there was no need for that force to include US troops.
"In fact, ideally for the kind of issues we are confronting there, the only truly effective force that will actually be able to reject Isil (IS) from within its own population is a force comprised of Iraqis and Kurds and moderate Syrian opposition," he said.
After seven hours of debate, British MPs overwhelmingly voted in favour of air strikes, and six RAF Tornados could be called into action over the weekend.
Prime Minister David Cameron told MPs: "This is about psychopathic terrorists that are trying to kill us and we do have to realise that, whether we like it or not, they have already declared war on us."
Denmark's government has agreed to send seven F-16s, while Belgian lawmakers said they would send six.
White House spokesman Josh Earnest welcomed the "strong support" for the coalition showed by its Europeans allies.
More than 40 countries, including several from the Middle East, have offered to join in, US officials say.
The latest US strikes were carried out by both fighter jets and drones.
The tanks were destroyed in the oil-rich Deir al-Zour province, the US Department of Defense said in a statement.
It also said strikes in Iraq had destroyed nine IS vehicles and damaged others.
UK-based activist group the Syrian Observatory for Human Rights, which monitors the conflict in Syria, said the number of casualties was unclear.
Recent air strikes have been targeting oil facilities under IS control in both countries in order to reduce its income.
The militant group is earning an estimated $2m (£1.2m) a day from oil sales.
IS has killed three Western hostages in recent weeks.
On Thursday, the European Union's anti-terrorism chief told the BBC that about 3,000 Europeans had gone to join armed Islamist groups in the region.
Earlier, Spain's interior ministry said Spanish and Moroccan police had arrested nine people suspected of belonging to a militant cell linked to IS.
A statement from the ministry said the suspects belonged to a group based in the Spanish enclave of Melilla, on the northern coast of Africa, and the neighbouring town of Nador, in Morocco.
One of those arrested is reported to be Spanish; the rest are Moroccan nationals.
Earlier this week, the UN Security Council adopted a binding resolution compelling states to prevent their nationals from joining jihadists in 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