The US and its allies staged nine airstrikes on Islamic State (Isis) targets in Iraq and four in Syria from early on Friday through to early Saturday, the Combined Joint Task Force said in a statement.

The attacks in Iraq hit Isis tactical units, buildings, fighting positions, a rocket system and a facility where improvised explosive devices were made, the statement said. The strikes in Syria were near the city of Raqqa and destroyed tanks and a bunker.

Isis has been forced on the back foot by US-led air strikes, which began in Iraq on 8 August and in Syria on 23 September, including its defeat in the long battle for control of Kobani, a town on the border between Syria and Turkey.

On Friday, however, Isis fighters led a suicide attack on an airbase in Iraq where US and coalition troops are training Iraqi forces. Isis launched the attack after taking the nearby town of al-Baghdadi, their first territorial gain in months, the Pentagon said.

Most of the Isis fighters died in the attack, killed either by Iraqi government forces or by detonating their suicide vests, said Navy Rear Admiral John Kirby, the Pentagon spokesman, who added that no Iraqi or US troops were killed or wounded, and no US troops were involved in the gunfight.

It was also reported on Saturday that the supreme leader of Iran, Ayatollah Ali Khamenei, has responded to overtures from President Barack Obama amid nuclear talks by sending the US president a secret letter.

Co-operation against Isis, in the event of a nuclear deal being secured, was reported to be at issue.