Kathy Gannon, 60, who was born in Timmins, Ont., and her colleague Anja Niedringhaus, 48, were on assignment for the Associated Press news agency when the incident occurred on the outskirts of Khost.
Gannon, shot three times in the attack, underwent surgery and was reported in stable condition, according to the news agency.
Niedringhaus, an internationally acclaimed photographer, was killed instantly.
Gannon, who joined AP in the mid-1980s, has reported on Afghanistan for nearly three decades.
Considered the dean of foreign reporters in the war-wracked country, Gannon is known for her encyclopedic knowledge of the region and fearless pursuit of stories.
"Kathy Gannon's writing on Afghanistan helped shape my mental map of the country, and Anja Niedringhaus' pictures helped illustrate it," said Stephanie Levitz, a journalist with The Canadian Press who has reported from Afghanistan.
Gannon and Niedringhaus were in a convoy of election workers delivering ballots under the protection of the Afghan National Army and Afghan police when attacked.
Witnesses said they were in their own car with a freelancer and a driver waiting for the convoy to move when the unit commander walked up and opened fire on them.
The commander, called Naqibullah, surrendered and was arrested.
According to the provincial chief of police, Naqibullah, 25, told authorities his impromptu attack was to avenge the deaths of family members in a NATO bombing.
John Daniszewski, AP's vice-president and senior managing editor for international news, said Gannon and Niedringhaus often worked together as a team.
"Kathy Gannon is a brave and passionate journalist whose expertise and deep knowledge and experience of both Afghanistan and Pakistan have made her an indispensable authority on the region," Daniszewski said.
Murray Brewster, another Canadian Press reporter who has covered Afghanistan extensively, described her as "a colleague who was always so generous with her time and wisdom."
Globe and Mail reporter Les Perreaux called Gannon "one of those legendary reporters who never fails to be a generous mentor."
Gannon arrived in the Pakistani city of Peshawar in 1986.
Shortly after the 2001 U.S.-led invasion of Afghanistan, the Taliban allowed her and a colleague into the country — the only journalists let in.
They covered the bombing campaign from Kabul by candlelight, with Gannon at one point thrown across the room as a bomb landed near the AP bureau.
Gannon, who went to high school in Timmins before studying at Cambrian College in Sudbury, Ont., has said she knew early in her career that she wanted to travel abroad but realized her options were limited with the Canadian media.
"I sold everything I owned, which wasn't much, and set out to become the foreign correspondent I'd always wanted to be," she wrote in her 2006 book, "I is for Infidel, From Holy War to Holy Terror: 18 Years Inside Afghanistan."
Afghanistan's violence has touched Canadian journalists on several occasions.
Calgary Herald reporter Michelle Lang was killed when the troop carrier she was in rolled over a roadside bomb in December 2009. Before that, Toronto Star reporter Kathleen Kenna was badly hurt in a grenade attack in 2002, while Radio Canada reporters, Patrice Roy and Charles Dubois, were seriously wounded by an improvised explosive device in 2007.
Gannon has been repeatedly recognized for her work. She won the International Women's Media Foundation Courage in Journalism award in 2002 and received the Edward R. Murrow fellowship from the Council on Foreign Relations during 2003-2004.
-With files from Associated Press.