The five children were among 11 people who died Friday when a roadside bomb struck their vehicle in the Spin Boldak district of southern Kandahar province near the border with Pakistan, according to police Gen. Saifullah Hakim.
The victims, all members of an extended family, were traveling to a local Muslim religious shrine for Friday prayer services, Hakim said.
Kandahar is the birthplace of the Taliban, and Hakim blamed the Islamic militants who plant bombs along roads in the area to target Afghan and foreign troops for Friday's blast.
"Innocent civilians are dying as a result," he said.
In London, the British Ministry of Defense announced that a British soldier was killed Thursday when a bomb exploded near a foot patrol in Gereshk, an industrial city of Helmand province where fighting has been raging this month. The soldier's death brings to 48 the number of NATO soldiers killed in Afghanistan in July - the deadliest month for the international force since the war began in 2001.
The U.S. command, meanwhile, reported that Afghan and U.S. soldiers killed 10 insurgents Friday in Kunar province of eastern Afghanistan. There were no international soldiers killed but the U.S. statement made no mention of Afghan army casualties.
U.S. commanders had been expecting bigger losses since President Barack Obama ordered 21,000 additional U.S. troops to Afghanistan this year to curb a resurgent Taliban, which was ousted from power in the U.S.-led invasion of 2001.
About 59,000 U.S. troops are in Afghanistan, and the number is expected to rise to at least 68,000 by the end of 2009. The total international force numbers about 91,000 troops from 42 nations.
But the rising casualty tolls have prompted U.S. and British officials to consider whether to send more troops to Afghanistan to bolster security, especially around the Aug. 20 presidential election. Britain has about 9,000 troops in Afghanistan, including 700 sent this year to augment security for the election.
The chief of the British army, Gen. Richard Dannatt, said there was a case to be made for "a short-term uplift" in troop numbers until Afghan forces are properly trained and deployed - which he said could take another 12 to 18 months. He told BBC Radio that scaling down troop levels after the Afghan election would be the "wrong thing to do."
On Thursday, U.S. Defense Secretary Robert Gates said the U.S. could send more troops to Afghanistan this year than had been initially planned, although any increase would not be significant. The Obama administration had wanted to wait until the end of the year to decide whether to send more troops.
The new commander of U.S. and NATO forces, Gen. Stanley McChrystal, is nearing the end of a 60-day review of troop requirements in Afghanistan and will forward his recommendations to Washington.
Also Friday, a suspected U.S. missile strike killed at least five alleged militants in a remote area of Pakistan near the border with Afghanistan, Pakistani officials said. The U.S. has launched dozens of missile strikes in Pakistan's northwest border regions, which are used as safe havens by Taliban and al Qaeda fighters to launch attacks against American and NATO forces in Afghanistan.
Two separate bombs in northwest Pakistan damaged a pair of oil tankers headed for NATO forces in Afghanistan, police said.
The attacks occurred along a major transit route for fuel and supplies headed to U.S. and NATO troops in Afghanistan.