A rocket crashed through the roof of the BBC's bureau in Baghdad today causing structural damage but no injuries.

It was one of a number of rockets fired towards the heavily fortified Green Zone by Shia insurgents taking advantage of a sudden sandstorm, which gave them cover from counter-attack by US aircraft.

Patrick Howse, the BBC's Baghdad bureau chief, said the rocket impacted at 2.45pm local time, leaving a hole around 1 metre by 1.5 metres in the roof of the office.

“It caused structural damage but no one was injured," Mr Howse said.

US and Iraqi forces blame Shia insurgents for firing rockets in the direction of the Green Zone from their power base of Sadr City, a teeming slum that is a stronghold of the Mehdi Army militia loyal to Moqtada al-Sadr, the Shia cleric.

In a bid to limit their ability to launch rocket attacks, US and Iraqi troops are building a wall in the southern part of the Sadr City district, which is expected to be completed within two weeks.

The barrier is intended to cut off militias from the outside world and enable the military to exert more control.

In other developments, the leader of al-Qaeda in Iraq remains a free man after the US military denied Iraqi reports that he had been captured.

Iraqi officials last night said that the militant, called Abu Ayyub al-Masri, had been arrested in the northern city of Mosul. In yet another false alarm, however, it turned out that a man with a similar name had been seized instead.

“Neither coalition forces nor Iraqi security forces detained or killed Abu Ayyub al-Masri. This guy had a similar name,” said Major Peggy Kageleiry, a US military spokeswoman in northern Iraq.

There have been false alarms in the past about al-Masri, the nom de guerre of Abu Hamza al-Muhajir. In 2006 and May 2007 reports circulated that he was dead, but they were later proved incorrect.

Al-Masri, whose nickname literally means “the Egyptian”, took command of al-Qaeda in Iraq after the US military killed his blood-stained predecessor, Abu Musab al-Zarqawi, a Jordanian former criminal turned Islamic fundamentalist. Al-Zarqawi, who is believed to have personally beheaded the British hostage Kenneth Bigley in 2004, was killed in a US air strike on his hide-out in June 2006.

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