The advance of Islamic State fighters on Kobani stalled on Thursday, Oct 16 according to a monitoring group, after U.S.-led coalition warplanes launched their heaviest bombardment yet on the militants, who have been assaulting the Syrian border town for nearly a month, Reuters reported.

Last week Turkish and U.S. officials said Islamic State were on the verge of taking Kobani from its heavily outgunned Kurdish defenders, after seizing strategic points deep inside the town.

A dramatic ramping up of coalition air strikes reached a new crescendo in recent days, with Islamic State targets around Kobani being hit nearly 40 times in 48 hours. The barrage has halted the militants' advance, with Kurdish sources saying that Kurdish YPG fighters had managed to retake some territory.

The four-week assault has increasingly been seen as a key test of U.S. President Barack Obama's air strike strategy, and Kurdish leaders have repeatedly said the beleaguered town cannot survive without arms and ammunition reaching the defenders, something neighboring Turkey has so far refused to allow.

Islamic State has been keen to take the town to consolidate its position in northern Syria after seizing large amounts of territory in that country and in Iraq. A defeat in Kobani would be a major setback for the Islamists and a boost for Obama.