Iran is ready to assist the Iraqi government in its battle against extremist Sunni insurgents, President Hassan Rouhani has said.

He denied Iran had sent troops to fight in Iraq. However, an Iraqi source told the BBC that 130 Iranian Revolutionary Guards had entered the country to provide military training and advice.

The insurgents have seized several cities and are closing in on Baghdad.

They regard Iraq's Shia majority as "infidels".

The Islamic State in Iraq and the Levant (ISIS) is a hardline Islamist militant group that grew during the US-led occupation (2003-2011).

It is one of several jihadist militias fighting the rule of Bashar al-Assad in neighbouring Syria.

Iran has close ties with Iraq's Shia-dominated leadership under Prime Minister Nouri al-Maliki.

Iraq's Sunni minority - which was dominant until 2003 - has complained of marginalisation by Mr Maliki's government.

"If the Iraqi government asks us for help, we may provide any assistance the Iraqi nation would like us to provide in the fight against terrorism," President Rouhani said on Saturday.

"However, the engagement of Iranian forces has not been discussed. Providing help and being engaged in operations are different."

Answering a question from the BBC, he said that so far the Iraqi government had not requested help from Iran.

President Rouhani did not rule out co-operating with the United States, Iran's traditional foe, in combating ISIS: "We can think about if we see America starts confronting the terrorist groups in Iraq or elsewhere."

BBC