Iraq's military is trying to staunch spillover from Syria’s crisis, tightening border controls as its troops exchange fire with gunmen, rockets hit a frontier patrol and Syrian army shells land on an Iraqi border town.

Iraq’s army last week took over frontier operations. A border crossing to Syria’s Albu Kamal is temporarily closed as Syrian forces backed by aircraft and rebels fight to control the town, which sits on key supply routes from Iraq.

Spillover from Syria worries an Iraqi government struggling to overcome its own insurgency and legacy of sectarian violence. Baghdad acknowledges that Sunni Islamist fighters are crossing the porous border to fight against President Bashar al-Assad.

Syria’s 17-month revolt is focused for now on the capital Damascus and Aleppo, but rebels are also battling for Albu Kamal, a strategic town that would allow them freer control of border supply routes.

Local Iraqi officials say Albu Kamal is mostly under the control of anti-Assad rebels, but Syrian security forces still hold a base and airfield outside the town, which keeps Assad’s opponents from taking the Syrian border.

“The military base outside Albu Kamal is still under the control of the Syrian regular army, and the Syrian planes and artillery kept bombing the city during the night and this morning,” said Farhan Ftaikhan, mayor of Al Qaim, the Iraqi city neighbouring Albu Kamal.

Iraqi troops protecting the porous border were targeted by two rockets near Al Qaim border crossing two days ago, but there were no injuries, authorities said over the weekend.

Iraqi forces came under fire again early yesterday morning. It was not clear who shot at them. Last week, a stray Syrian army shell landed in Al Qaim, damaging a building, but causing no casualties.

An Iraqi army battalion has taken over control of the frontier from regular border forces as a precautionary measure, said Mohamed Fathi, spokesman for the governor of Anbar province, Iraq’s western desert region straddling the Euphrates.

Close to Assad’s main ally, Shia power Iran, Baghdad finds itself in a balancing act over Syria’s crisis. Prime Minister Nuri al-Maliki was re-elected in 2010, thanks in part to Iran’s support for Iraqi Shia political parties.

Among Iraq’s Shia leadership, however, there may be little love for Assad, whose government Iraq had blamed for allowing insurgents and suicide bombers to cross over from Syria to attack US and Iraqi troops at the height of the war.

The Iraqi leaders are uncertain of the impact on Iraq’s own delicate sectarian makeup should Assad fall. Maliki faces lingering sectarian infighting among Iraq’s own Shia, Sunni and Kurdish political blocs.