Iran on Thursday warned a key international conference that a long-term U.S. military presence in Afghanistan would fan regional insecurity and could plunge the war-torn country back into further chaos.

Representatives from 29 countries gathered in Kabul for the conference, weeks after NATO agreed at a summit in Chicago to stick to plans to withdraw the bulk of 130,000 foreign combat troops from Afghanistan by the end of 2014.

Afghan President Hamid Karzai on Tuesday said NATO had agreed not to carry out air strikes on residential areas even in self-defense, apparently contradicting comments made by senior coalition commanders.

NATO's International Security Assistance Force (ISAF) ordered an end to air strikes on homes except as a last resort to ensure the defense of troops, Lieutenant General Curtis Scaparrotti, deputy commander of U.S. forces, said on Monday.

Afghan President Hamid Karzai said Saturday that the U.S. commander of NATO forces in Afghanistan had "promised" air strikes on residential areas would stop after apologizing for recent civilian deaths.

Karzai met General John Allen, commander of NATO's International Security Assistance Force (ISAF), and U.S. Ambassador Ryan Crocker days after a strike in Logar province, which Afghan officials say killed 18 civilians.

Afghan President Hamid Karzai Thursday condemned as unacceptable a NATO air strike that killed 18 civilians and would cut short a trip to Beijing to return home, his office said.

"Attacks by NATO that cause life and property losses to civilians under no circumstances could be justified and are not acceptable," Karzai said of the attack Wednesday in Logar province south of Kabul.

U.S. Defense Secretary Leon Panetta told troops in Afghanistan on Thursday that the decade-long war was at "a turning point", as Kabul reacted with fury to a NATO air strike that killed up to 18 civilians.

Panetta arrived in the Afghan capital on his second visit in less than three months.

The number of civilians killed in the Afghan war in the first four months of this year has dropped by 21 percent over the same period in 2011, the United Nations said Wednesday.

A total of 579 civilians died and 1,219 were wounded, with insurgents responsible for the vast majority of the deaths, Jan Kubis, the U.N. special representative for Afghanistan, told a news conference.

Afghanistan's parliament on Saturday voted by an overwhelming majority to ratify a strategic partnership agreement with the United States signed earlier this month, lawmakers said.

"We voted with a majority in favor of the strategic pact," MP Shukria Essakhil told AFP.

Afghan intelligence agents on Wednesday arrested five suicide bombers with hundreds of kilos of explosives near Kabul international airport.

"We have arrested five suicide attackers with 560 kilograms of explosives in a minivan just near the gate of Kabul international airport," National Directorate of Security (NDS) spokesman Lutfullah Mashal told Agence France Presse.

Seven people were killed and 12 others wounded in a suicide attack on the governor's compound in Afghanistan's western Farah province on Thursday, police said.

"Seven people -- six policemen and one civilian -- were killed and 12 others were wounded, including nine civilians and three police," regional police spokesman Abdul Raouf Ahmadi said.

A Taliban-type improvised bomb ripped through a bazaar in a remote town in northwestern Afghanistan Monday, killing seven civilians and injuring eight others, police said.

The blast in Ghormach district in the province of Faryab was the latest in a string of deadly bombings and suicide attacks since Taliban insurgents announced the start of their spring offensive earlier this month.