A double car bombing ripped through a crowded Baghdad market on Sunday, killing at least 56 people and wounding scores more in a first vicious blow to the city's new US-led security operation.
"Where is the security plan?" wailed distraught relatives crowded outside the Iraqi capital's Kindi Hospital, as fleets of ambulances and civilian trucks ferried the dead and dying into an overworked emergency room.
Kindi received 42 corpses — including 10 children aged between five and 10 — and was treating 83 seriously wounded patients, medics said.
Ibn Nafees Hospital saw 14 dead and 20 critically injured men, women and children, a medic there said. The death toll seemed certain to rise.
A first explosion ripped through a crowded vegetable market in Baghdad Jadida, a mixed but mainly Shiite district of east Baghdad.
At almost the same moment, another booby-trapped car detonated a few hundred metres (yards) away near a row of electrical goods shops.
Desperate bystanders scoured the blackened debris for wounded loved ones, while shell-shocked bystanders loaded the injured into civilian vehicles.
In a separate attack in nearby Sadr City, a suicide car bomber attacked a checkpoint mounted by Iraqi police commandos, killing one policeman and wounding 10 more officers and four passers-by, a security official said.
Earlier, an unidentified sniper shot dead three civilians shopping in the Fadhel district of the city, according to a defence official.
Separately, the US military announced its first casualties since the launch of the plan -- two soldiers killed in north Baghdad on Saturday, one by an insurgent's grenade, the other by small arms fire.
Car bomb attacks in east Baghdad are the hallmark of Sunni extremists targeting Shiite civilians in the Iraqi capital's vicious sectarian war.
Last Monday, at least 79 people were killed in similar attacks on Shiite markets, but the violence had tailed off since the launch of a large-scale security operation by US and Iraqi forces on Wednesday.
Shortly before the blasts, the commander of Iraqi forces involved in the operation, General Abboud Gambar, had toured parts of Baghdad Jadida with reporters to demonstrate the progress made by his forces.
"I want to tell the people, from this place, that security is coming to Baghdad," Gambar told reporters. "We will chase the terrorists out of Baghdad."
Nevertheless, junior security minister Shirwan al-Waili, warned: "The security plan will take a long time, because the terrorists are an enemy with a long term strategy."
As their heavily-armed 20-vehicle convoy left the area, smoke could already be seen rising over the market.
Meanwhile, Iraq started to reopen its borders with Iran and Syria, which had been closed temporarily three day earlier to allow security equipment and procedures to be updated as part of the security plan.
"We received orders today from Prime Minister Nuri al-Maliki to open the border posts from 6:00 am (0300 GMT) this morning," General Rahdi Mohassen of the Iraqi border force told reporters at the Shalamchen border post.
A senior security official in Baghdad confirmed that two main routes into Syria and four into Iran had reopened. Other routes will remain closed for the time being, with more opening in the coming days, officials said.
The United States, which has 140,000 troops in Iraq, accuses Iran and Syria of allowing militants and weapons to be smuggled into their neighbour to carry out attacks on US and government forces and Iraqi civilians.
Iran and Syria deny the charge.
The closure was part of a broader operation in which thousands of extra US and Iraqi troops have been sent into Baghdad, the epicentre of a vicious civil war between rival Sunni and Shiite factions.
"Nearly 20,000 security patrols were conducted this week," said US spokesman Lieutenant Colonel Scott Bleichwehl. "Since the operation started, there has been a reduction in the number of attacks across the Iraqi capital."
US officials did not offer any figures for the number of attacks recorded, and have been careful not to raise hopes of a rapid victory, but an Iraqi military spokesman said Saturday that violence was down 80 percent.