The Afghan government on Wednesday lashed out at U.S. efforts to broker peace with the Taliban, suspending crucial security talks with Washington and threatening to boycott prospective contacts with the insurgents in Qatar.

Kabul issued two strongly worded statements threatening to sabotage U.S. efforts to start talks with the Taliban, just one day after its foes opened an office for dialogue in the tiny Gulf emirate.

Afghan government envoys are to travel to Qatar to try to open peace talks with the Taliban on a possible deal ending 12 years of conflict, President Hamid Karzai said Tuesday.

Karzai's announcement was a boost for the moribund peace process, which has made little ground despite mounting pressure as the withdrawal of 100,000 NATO troops from Afghanistan looms next year.

President Hamid Karzai on Tuesday announced the transfer of nationwide security from NATO to Afghan control, a major milestone as the U.S.-led war effort winds down after 12 years.

Shortly before Karzai's speech at a handover ceremony, the location of which had been kept a secret, a prominent lawmaker escaped a bomb attack in Kabul that killed three civilians, underlining the country's continuing instability.

Afghan security forces will soon take over responsibility for the whole of the country, officials said Saturday, a major milestone as the NATO-led war effort winds down after 12 years of fighting.

The handover of the last 95 districts from NATO to Afghan forces includes many of the most volatile areas of south and east Afghanistan where the Taliban have fought a bloody insurgency against the U.S.-backed government since 2001.

The NATO commander in Afghanistan warned Friday that gains secured in 12 years of fighting could be lost if donor nations cut back support when troops leave next year.

Billions of dollars in military and civilian aid have been promised to Afghanistan after the NATO-led combat mission ends, but many Afghans fear they will be abandoned by the war-weary international community.

Afghan President Hamid Karzai said on Sunday the Muslim world was "in turmoil" and wondered whether the "war on terror" led by the United States since 2001 was to blame for the radicalization.

Addressing a forum on relations between the U.S. and the Muslim world in Doha, Karzai declared: "The war on terror as it began in 2001 and moved forward until today has not been a happy one."

Afghan President Hamid Karzai on Sunday visited Qatar for talks with officials in the wealthy Gulf state that could host future peace negotiations between the Afghan government and Taliban insurgents.

With U.S.-led NATO combat troops due to withdraw from Afghanistan by the end of 2014, Karzai recently backed a proposal for the Taliban to open an office in Doha, the Qatari capital.

A roadside bomb killed a father and three of his children in western Afghanistan on Tuesday, the latest of a recent spate of civilian casualties in the 12-year war.

The United Nations mission in Kabul said on Monday that in the past two weeks, 125 Afghan civilians had been killed and 287 injured in the conflict, a 24 percent increase from the same period in 2012.

Afghan President Hamid Karzai will seek greater Indian military aid from India during a visit this week to New Delhi, officials of both countries said Monday.

India has provided billions of dollars of aid to Afghanistan since the fall of the Taliban in 2001, and is keen to ensure that no radical Islamist regime takes power in Kabul after international troops pull out in 2014.

A bomb killed 13 civilians including women and children in southern Afghanistan on Monday as they traveled to attend the funeral of earlier bomb victims, police said.

It was the latest violence since the Taliban launched their annual "spring offensive" on April 27, opening a crucial period for the country as its security forces take the lead in offensives against the insurgents.