Read Deborah Haynes's blog on life in Iraq

A twin suicide bombing killed 14 people in Baghdad today, including the leader of a key Sunni Arab security patrol, further tarnishing a period of relative calm across the country and raising fears of a return to darker days.

In the morning attack blamed on al-Qaeda, one bomber detonated an explosive vest outside the office of a government agency that looks after Sunni mosques and shrines. Minutes later, the second assailant set off a car bomb as people fled from the Sunni Endowment office in Baghdad’s northern Adhamiyah district.

The double explosions were the latest in a string of bombings to rock Iraq in the past fortnight despite a 60 per cent drop in overall violence since the summer.

Mourners carried the bodies of Colonel Riyadh al-Samarrai, the security leader, and some of his bodyguards through the streets of Adhamiyah, once a Sunni insurgent hotbed until the colonel and his patrols started work under the pay of the US military.

"The martyrdom of the colonel is an inspiration to us now. All of us will become Colonel Riyadhs," said Abu Firas, a member of the area's "awakening" movement, the Iraqi name for Sunni Arab tribes that have turned against al-Qaeda. At least 28 people were wounded in the two blasts.

Civilian security patrols, like those led by Colonel Samarrai, have sprung up in insurgency strongholds, with armed guards, bankrolled by the US military, manning checkpoints and securing mosques and schools. They are cited as a central factor in the reduction of violence.

But the success of the “awakening” movement has turned its predominately Sunni Arab members, thought to number more than 70,000, into prime targets for anti-government and anti-US fighters.

Osama Bin Laden has warned Iraq’s Sunni Arabs against joining the "awakening" groups or taking part in a unity Government.

As well as the double bombing today, gunmen killed a member of another civilian security patrol in the central Iraqi city of Samarra.

In further violence, a bomb in a market cart in central Baghdad and two roadside bombs in the southern Jadiriyah district killed five people, while police said that the bodies of five men handcuffed, blindfolded and shot in the head were found in volatile Diyala province,

The fresh bloodshed aroused fears among some Iraqis in Baghdad that an undeniable improvement in the security in parts of the city, which has encouraged shops to reopen and some refugees to return home, is only temporary.

“I am very sad,” said Ali Fadhel, 26, who owns a mobile phone shop in the capital.

“There is much life in the streets and the shops are open but people are still afraid of the militia … Also the bombs have started to kill civilians again,” he said.

The planned withdrawal of more than 20,000 American troops by July, as the US "surge" – cited as a central factor in the reduction in violence – comes to an end, has prompted cause for concern as well as the sustainability of a ceasefire by al-Mahdi Army members loyal to Hojatoleslam Moqtada al-Sadr, the powerful Shia cleric.

“The American troops will start to withdraw this year and I am sure that will cause a big civilian war, without a doubt,” said Mr Fadhel.

Abid al-Jabr, 21, a student who works part-time at a pharmacy, is more optimistic, but he feels that the drop in violence prompted Iraqi soldiers and police to relax, enabling bombers to catch them off guard in the recent spate of attacks.

“I do see that the situation is improving and this is the main aim for the Government in 2008,” he said.

Separately, a fire at Iraq's main oil refinery in the northern city of Beiji killed one person. It was blamed on a technical fault.

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