Anne Smedinghoff, 25, was killed Saturday, April 6, 2013, in southern Afghanistan, the first American diplomat to die on the job since last year's attack on the U.S. diplomatic installation in Benghazi, Libya. (AP Photo/Courtesy of Tom Smedinghoff) (Uncredited/AP)

Three American civilians and three U.S. troops were killed in two attacks in Afghanistan on Saturday, officials said, including a powerful blast that struck officials traveling to a school to donate books. Among the dead was the first State Department diplomat to be killed in the country since the war began.

The bloodshed Saturday, the deadliest day this year for Americans in Afghanistan, underscored how dangerous the country remains as the United States proceeds with the withdrawal of its remaining troops over the next 20 months, leaving security in the hands of Afghanistan’s fledgling army.

The attacks suggested that even as the military coalition’s focus shifts to managing the drawdown, the United States appears likely to face an intense “fighting season,” the springtime period in Afghanistan during which violence typically in­creases.

The American diplomat killed Saturday was identified as Anne Smedinghoff by her parents. Smedinghoff was recently tasked with assisting Secretary of State John F. Kerry on his trip to Kabul.

Four other State Department officials who were with her, traveling to a school in the southern province of Zabul, were injured in the same bombing, one critically, Kerry said in a statement.

“She was everything a Foreign Service Officer should be: smart, capable, eager to serve, and deeply committed to our country and the difference she was making for the Afghan people,” Kerry said. “She tragically gave her young life working to give young Afghans the opportunity to have a better future.”

In a somber address to State Department employees in Istanbul, Kerry paid tribute to Smedinghoff.

There is no greater contradiction, Kerry said, between Smedinghoff's zeal to "change the world" and help others and a bomber who he said drove a car into their vehicle.

"Folks who want to kill people, and that's all they want to do, are scared of knowledge. They want to shut the doors," Kerry said.

"Here is a huge challenge for us. Here's a confrontation with modernity, with possibilities, with everything that our country stands for."

Smedinghoff, 25, served as Kerry’s main embassy guide and aide during his two-day visit late last month. That assignment, as a “control officer,” is considered an honor and a mark of promise for young Foreign Service officers.

The diplomat began an assignment as a press officer in Kabul last summer after spending two years at the U.S. Embassy in Caracas, Venezuela, where she worked in the consular section. Smedinghoff graduated from Johns Hopkins University with a degree in international relations, said her parents, Tom and Mary Beth Smedinghoff.

The Smedinghoffs, who live in the Chicago area, said in an e-mail that their daughter joined the State Department straight out of college.

“She particularly enjoyed the opportunity to work directly with the Afghan people and was always looking for opportunities to reach out and help to make a difference in the lives of those living in a country ravaged by war,” they said. “We are consoled knowing that she was doing what she loved, and that she was serving her country by helping to make a positive difference in the world.”

The attacks came as Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, arrived in Afghanistan to take stock of the war as U.S. officials continue to deliberate how quickly they should pull out the 68,000 American troops still deployed there.

Saturday’s violence followed a coordinated attack Wednesday in the country’s relatively safe west that killed at least 46 people. The Taliban claimed responsibility for the assault in Farah province, saying it had been carried out to avenge the group’s fighters who have been “kept in prisons for years on end and even mercilessly given the death penalty.”

In the deadlier of the two attacks Saturday, in Zabul province’s Qalat district, insurgents detonated a bomb when a convoy transporting U.S. troops and State Department officials and another one carrying the governor of the province intersected. The blast, in an area that has long been a Taliban stronghold, killed three U.S. service members, the young diplomat and a U.S. Defense Department employee.

The Associated Press reported that the governor survived the attack but that an Afghan doctor was killed in the explosion.

In a statement, the Taliban said the attack was carried out at noon when a militant detonated explosives packed in a vehicle as the provincial governor was approaching the Americans. A Taliban spokesman told the AP that militants linked to the group were hoping to strike a U.S. or an Afghan government convoy when they placed the bomb. “We were waiting for one of them,” spokesman Qari Yousef Ahmadi said. “It was our good luck that both appeared at the same time.”

In the east, meanwhile, a third American civilian was killed in an “insurgent attack,” according to a statement issued by the military coalition in Kabul. It offered no further details.

Dempsey, the country’s top U.S. military official, told reporters traveling with him that he was heartened by what U.S. officials have described as spontaneous rebellions against the Taliban that have unfolded in recent months as the U.S. presence in the country has thinned. He expressed hope that a political solution will lead at least some segments of the Taliban to join the political process, according to remarks published by the American Forces Press Service, a Pentagon news division.

“Any conflict in history, when it is resolved, is resolved through some form of reconciliation,” Dempsey said. “I support the effort to try . . . through the Afghans to encourage them to take reconciliation as an important line of effort.”

Kerry, who traveled Saturday to the Middle East, spoke to the woman’s parents to offer “what little comfort I can for their immeasurable loss.”

“As the father of two daughters, I can’t imagine what their family is feeling today,” he said.

Tom Smedinghoff said his daughter died in the pursuit of a career she loved.

“The world lost a truly beautiful soul today,” he said. “She was such a wonderful woman--strong, intelligent, independent, and loving.”

Anne Gearan contributed to this report.