* Security "dramatically deteriorated" in first two months of 2011
* Two children killed in foreign air raid-Afghan officials
* Civilian casualties at their highest since the war began (Recasts with ICRC report)
By Jonathon Burch and Hamid Shalizi
KABUL, March 15 (Reuters) - Life for ordinary Afghans has become untenable, the Red Cross said on Tuesday, with security seriously deteriorating in the first two months of the year due to a surge in Taliban attacks and accidental NATO strikes on civilians.
Violence in Afghanistan is at its worst since the Taliban were overthrown nearly a decade ago, despite the presence of around 150,000 foreign troops, and with Afghan forces to start taking over securing parts of the country in a few months.
The International Committee of the Red Cross (ICRC) said January and February were particularly bad for Afghans, with more suicide bombings in public places, more roads strewn with bombs and more international military operations gone wrong.
On Tuesday, Afghan officials said two children were killed in an air strike by NATO-led forces as they were watering fields in eastern Kunar province late on Monday.
"The first two months of 2011 have seen a dramatic deterioration in the security situation for ordinary Afghans," Reto Stocker, the head of the ICRC in Afghanistan, said in a statement.
"It is an untenable situation. Civilians must be protected from harm as much as possible, not become victims of the fighting."
Civilian casualties caused by NATO forces are a major source of tension between Afghan President Hamid Karzai and his Western allies. They also anger Afghans, complicating efforts to win their support for a war that, for most people, has brought only misery.
Abdul Marjan, district chief of Chawki in Kunar where the two brothers, aged 10 and 15, where killed, said the boys had been working on irrigation channels before they were hit.
"They might have been mistaken for insurgents as they were carrying spades on their shoulders," Marjan told Reuters.
Shahzada Shahid, a lawmaker from Kunar, said the pair were students who had gone out to help work their father's fields.
Irrigation agreements between villagers in the area mean the family's land gets access to river water only in the evening.
A spokesman for the NATO-led International Security Assistance Force,(ISAF) said an air strike in Chawki on Monday evening had targeted two suspected insurgents, killing one and wounding another after they were seen planting a roadside bomb.
He added ISAF was looking into media reports of civilian casualties.
The children's deaths come less than three weeks after two foreign helicopters gunned down nine boys as they collected firewood in the same province, a volatile area bordering Pakistan where international forces have stepped up operations in recent weeks.
The incident followed a spate of reported civilian deaths by foreign troops, mainly in the east, and prompted a sharp rebuke Karzai and a rare and candid apology for the killings by U.S. General David Petraeus, the commander of U.S. and NATO forces in Afghanistan.
U.S. President Barack Obama also expressed his "deep regret" over the killings and U.S. Defense Secretary Robert Gates, on a visit to Afghanistan last week, said the killings were a "setback" to bilateral relations.
Last year was the most lethal for civilians since the war started, with a 15 percent rise in civilian deaths to 2,777, according to a U.N. report last week. The report said insurgents were responsible for three-quarters of the deaths.
NATO-led forces have significantly tightened rules governing air strikes and night raids in the past two years, leading to a drop in civilian casualties, but deaths are still relatively frequent and highly sensitive.
The U.N. report found that, while there was a 52 percent decline in civilian deaths from air strikes in 2010 compared to 2009, there was a 48 percent rise in deaths in the second half of last year compared to the first half.
This was due to "significant increases" in the use of air power during the second half of 2010. (Editing by Miral Fahmy)
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