AFP - Relatives and colleagues of a young US diplomat killed in Afghanistan honored her as a smart woman just starting her career and eager to engage with locals in the war-ravaged country.

Anne Smedinghoff, 25, was among at least five Americans killed in separate attacks Saturday, in the deadliest day for foreigners in Afghanistan this year, as she traveled with Afghan officials to distribute books to students.

"She particularly enjoyed the opportunity to work directly with the Afghan people," her parents Tom and Mary Beth Smedinghoff said in a statement.

She "was always looking for opportunities to reach out and help make a difference in the lives of those living in a country ravaged by war," they added.

The last American diplomat killed on the job was US ambassador to Libya Chris Stevens.

He died along with three other Americans -- two embassy security personnel and an information officer -- in an attack on the US diplomatic mission in the eastern city of Benghazi on September 11.

Secretary of State John Kerry, traveling in Turkey, lashed out at the "cowardly" Taliban extremists who killed the "selfless, idealistic" young diplomat.

"Anne and those with her were attacked by Taliban terrorists who woke up that day not with a mission to educate or to help, but with a mission to destroy," Kerry said during a press conference with Turkish Foreign Minister Ahmet Davutoglu.

"A brave American was determined to brighten the light of learning through books written in the native tongue of the students that she had never met, but whom she felt compelled to help."

Kerry met Smedinghoff when she assisted him during a visit to Afghanistan two weeks ago.

At least three US soldiers and another civilian were killed in the attack that saw a suicide car bomber strike a NATO convoy in the southern province of Zabul. Four other State Department employees were injured, one critically, according to officials.

Another US civilian was killed in a separate assault in eastern Afghanistan.

Speaking to staff and families at the US Consulate General in Istanbul, Kerry acknowledged that such attacks pose a "huge challenge" as US troops and their NATO allies prepare for a withdrawal at the end of next year.

"It's a grim reminder to all of us, though we didn't need any reminders, of how important and also how risky carrying the future is... and just trying to provide opportunity to those young boys and girls and men and women in Afghanistan."

Flags and white ribbons lined the street of Smedinghoff's family home in River Forest, a suburb of Chicago, local media reported.

Smedinghoff's first assignment as a diplomat was in Caracas before she volunteered to work in Afghanistan starting in July as a public diplomacy officer.

Her parents said she had joined the US Foreign Service right after graduating from college in 2009 and loved her work, despite the risk.

"We always knew in the back of our minds that this was a possibility. She went everywhere. She usually told us about it afterward, but she never expressed any fear at all," her father told CBS News.

In their statement, Smedinghoff's parents said they were "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."

In addition to her parents, Smedinghoff is survived by a brother and two sisters.

She graduated from Johns Hopkins University with a degree in international studies, and rode in an annual cross-country bicycle trip organized by students and alumni to raise money for cancer patients.

"I think living in Afghanistan is dangerous 24/7," her aunt Rita Carter told the Chicago Sun-Times. "Anne downplayed it because this was how she was going to save the world."