Air strikes carried out by the US-led coalition on Islamic State (IS) have inflicted "significant" damage on the group's capabilities, US Secretary of State John Kerry says.

Mr Kerry said the campaign against the militant group could take years, but that the coalition would remain engaged "as long as it takes".

The US said earlier that Iran, not a coalition member, had carried out air strikes against IS in Iraq.

However, Iran has denied this.

The US said there had been no coordination with the Iranians on any air strikes.

IS controls large areas of Syria and Iraq, imposing a rigid version of Sunni Islam and persecuting or killing non-believers.

BBC