Despite heavy clashes there is no sign of imminent military moves by the US as officials mull over intervention

Iraqi government forces fought off jihadi rebel forces north of Baghdad on Tuesday amid signs from the US that the Obama administration is hesitating before being drawn into a new war.

Heavy clashes were reported from Baquba after it was taken over by fighters of the Islamic State in Iraq and the Levant (Isis), and in Baghdad eight people were killed by a suicide bomber. Iranian-backed militiamen were out in force in Shia areas of the capital in an attempt to assure residents that they have a highly volatile situation under control.

As the fighting continued, there was no sign of imminent military moves by the US, with the White House warning of several days of further consultation before any intervention. Senior Democrats have expressed growing caution about the risks of being sucked back in to any conflict.

In London David Cameron warned that Isis militants in Iraq and Syria were the "biggest threat to national security that exists today", as Britain announced plans to reopen its Tehran embassy, closed since an attack in 2011. William Hague, the foreign secretary, said the UK and Iran shared an interest in stability in the region. He also described talk of joint military action in Iraq as "far too ambitious and unrealistic".

The UK-Iranian rapprochement has been in the making for months following last year's Iranian election, President Hassan Rouhani's more conciliatory approach, and an interim agreement on Iran's civil nuclear programme. But it was given an urgent push by the need to try to involve Iran in stabilising Iraq.

Hague's announcement came amid reports of the clashes in Baquba, less than 40 miles north of Baghdad, and the closest the fighting has come to the Iraqi capital since Isis took over most of the northern part of the country last week. Insurgents had taken control of parts of Baquba overnight, but were pushed back. Associated Press said 44 Sunni detainees were executed by pro-government Shia militiamen after Sunni insurgents reportedly tried to storm the jail near Baquba, but the Iraqi military put the death toll at 52 and said the Sunni prisoners were killed by mortar shells.

There were reports, too, that Sunni insurgents have attempted to target convoys of Shia volunteers being bussed to the front lines north of the capital.

Fighting was also reported near Kirkuk in northern Iraq, where an attack by militants was repelled after an hour of clashes.

The swift advance of Isis backed up by other disaffected Sunnis has faced little opposition from US-trained Iraqi forces, triggering fears that the extremists will end up controlling a swath of territory from eastern Syria to northern Iraq.

Iraq's prime minister, Nouri al-Maliki, was reported to have fired several senior security force commanders over their failure to halt the insurgent offensive.

In Washington there were signs that Barack Obama is wary over calls for air strikes. Spokesman Jay Carney said the president would "continue to consult his national security team in the days to come". Obama met his advisers on Monday evening after announcing a bolstering of the US embassy security presence in Baghdad, but has repeated his concern that military support of the Iraqi government would be of little use without a longer-term political plan to unite the country.

"The president asked his national security team to develop options and that effort continues," Carney told reporters during a briefing on Air Force One. "The president made clear that in his view … there is not a military solution to Iraq's problems," he added. "There is a near-term challenge presented by the movement of ISIL [Isis] … and we are assessing that situation … we will continue to do that and continue to look at options to assist [the Iraqi security forces]."

Carney declined to discuss a timeframe for any intervention, and although it is still possible that a surprise intervention could be launched, there are signs that pressure for action from Congress may be reversing.

On Monday night the Obama administration ordered the urgent deployment of several hundred armed troops in and around Iraq, after the insurgency forced the first, albeit brief, talks in more than a decade between the US and Iran over a common security interest.

As Obama weighs up his options on how to prop up Maliki's Shia-led government, Iran is already deepening its involvement in Iraq. Qassem Suleimani, commander of Iran's Quds force, is in Baghdad providing advice on how to deal with Isis and the Sunni insurgency. In an intriguing hint of possible cooperation, Iraqi security officials said the US had been notified in advance of the visit by Suleimani, whose forces are a branch of Iran's Revolutionary Guard and have organised Shia militias to target US troops in Iraq and, more recently, have helped the Syrian president, Bashar al-Assad, in his civil war.

Zuhair al-Nahar, a spokesman for Maliki, appealed for help from the US and the UK. "The government and the armed forces and the volunteers have stopped any advance of the Isis terrorists," he told the BBC. "The Iraqi air force is carrying out continuous sorties and attacks on convoys and strategic areas of the terrorists. However, Iraq needs all the support it can get. Iraq has asked the US for air strikes to be conducted. Iraq would like support in counter-terrorism, intelligence activities and advice and training."

Additional reporting by Mark Tran and Spencer Ackerman

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