Yousafzai called on Nigerian authorities and the international community "to do more" to free the more than 200 schoolgirls.
Population increases that have outpaced economic growth are among the contributing factors, observers say.
Many had hoped "Mama Taraba" would make history in a state election, but she ultimately lost at the polls.
Ekiti state governor Ayo Fayose is no stranger to legal challenges by the opposition party, the All Progressives Congress (APC).
Boko Haram fighters have killed thousands of people in their six-year bid to create an Islamist caliphate in northeastern Nigeria.
Government search efforts have been unsuccessful despite a global social media campaign and pleas from international leaders.
This is the second time Nigeria's election commission has declared the gubernatorial election in the southeast state inconclusive due to irregularities.
Voter apathy and the fear of violence at polling stations reportedly kept many Nigerians at home.
A researcher at NASA's Jet Propulsion Laboratory in California chose to name her discovery after the young Nobel Peace Prize recipient.
As many as six people may have been killed in violence related to gubernatorial elections Saturday.
The addition of rickshaws is one of many ways Uber is trying to compete in emerging markets around the world.
The Peoples Democratic Party warned Thursday that members of the All Progressives Congress plan to rig Saturday's voting.
In the African country, "unfortunately, they are more tolerant of some deaths than we would be in the U.S," an observer said.
"Those defecting from the PDP, based on the outcome of the presidential and national assembly elections, lack principles of integrity and morality. They are indeed stomach politicians.”
The All Progressives Congress accused the Peoples' Democratic Party of cheating during the presidential election.
Some Muslims said they were afraid to go home because of harassment from their Christian neighbors.
After losing national elections, the Peoples Democratic Party must win state-level races Saturday -- or face possible collapse.
The oba, or king, of Lagos threatened the Igbos with death if the ethnic group doesn't vote for the All Progressives Congress candidate on Saturday.
Hundreds of Kenyan students marched Tuesday to honor those killed last week in the attack at Garissa University College in northeast Kenya.
The All Progressives Congress blamed the alleged deaths of their Rivers state members on the Peoples Democratic Party in Nigeria.
"In a way, it's confirmation of what many of us had quietly feared for some time," said J. Peter Pham, director of the Africa Center at the Atlantic Council.
"If you go against my wish, you will perish in the water," the Oba of Lagos, Rilwan Akiolu, told the Igbos.