Britain, Denmark and Belgium join air campaign against Islamic State in Iraq

LONDON — Three European nations — including Britain — joined the widening U.S.-led air campaign against Islamic State militants in Iraq on Friday, even as the group’s fighters renewed their attempt to overrun a strategic border city in Syria.

Britain’s entry seven weeks after the United States began carrying out strikes followed an overwhelming parliamentary vote to authorize attacks. Denmark and Belgium also opted to join the fight.

But as the coalition expanded, its constraints became clear. All three countries that authorized military action Friday are limiting their roles to Iraq. Meanwhile, Islamic State militants demonstrated that airstrikes have failed to slow their assault on critical positions in Syria.

Along the Turkey-Syria border, Islamic State fighters backed by artillery fire pushed toward the city of Kobane — known in Arabic as Ayn al-Arab — as Syrian Kurdish forces dug in for a key test of their strength.

The United States and its Arab allies broadened their campaign to targets in Syria this week after a drumbeat of U.S. strikes in Iraq since early August.

But no European ally has been willing to join the Syria campaign — raising the prospect that the Islamic State could try to use the country as a refuge.

“Simply allowing [the Islamic State] to retreat across an invisible border is no answer,” said Peter Hain, a member of Parliament and former cabinet minister, during Britain’s day-long debate.

British Prime Minister David Cameron, scarred by a humiliating defeat last year when he sought permission to launch strikes against the government of Syrian President Bashar al-Assad, did not try to win approval for attacks in Syria this time around.