"Please know this: we will never forget you. We will always stand with you," 17-year-old Yousafzai wrote in an open letter to the missing girls. "We will not rest until you have been reunited with your families."
               
Yousafzai was shot in the head on a school bus in Pakistan by the Taliban in 2012 for refusing to quit school and won global acclaim for her passionate advocacy of women's right to education.

READ MORE: Atleast 2,000 women and girls kidnapped by Boko Haram: Amnesty
               
Last year, she was awarded the Nobel Peace Prize jointly with Indian children's rights activist Kailash Satyarthi.
               
In her letter, Yousafzai called on Nigerian authorities and the international community "to do more" to free the more than 200 schoolgirls abducted by Boko Haram Islamist militants a year ago.


               
Their abduction from a secondary school in Chibok in the country's Northeast last April drew international attention to the humanitarian crisis caused by attempts by the militants to establish a medieval-style caliphate in religiously mixed Nigeria.
               
Celebrities, including U S singer-songwriter Mary J Blige and First Lady Michelle Obama, joined in a global #BringBackOurGirls campaign last year to draw attention to the kidnapping as public outrage spread across the world.

Also Read: Malala criticises world leaders on Boko Haram kidnappings
               
While some of the girls managed to escape the militants' grip, the majority of them remains missing.
               
"In my opinion, Nigerian leaders and the international community have not done enough to help you," wrote Yousafzai.


               
On the occasion of the one-year anniversary of the kidnapping on Tuesday, Nigeria's President-elect Muhammadu Buhari vowed to make every effort to rescue the girls, but conceded that it was not clear whether they would ever be found.
               
Earlier this week, Amnesty International said in a report that Boko Haram has kidnapped at least 2,000 Nigerian women and girls since the start of 2014, many of whom were sexually abused or trained to fight.
               
In July last year, Yousafzai visited some of the abducted girls' parents in Nigeria and met five girls who had escaped the kidnapping.

ALSO READ: UN pledges support to Nigeria to defeat Boko Haram
               
"Your parents are grief-stricken. They love you, and they miss you," she wrote to the missing girls.
               
However, she said there were reasons to be optimistic about rescuing the girls and encouraged them to "never lose hope."
              
To mark the anniversary of the kidnapping, The Malala Fund, the charitable organisation founded by Yousafzai and her father Ziauddin to empower girls through education, launched the #DearSisters initiative to gather messages of hope and support for the abducted girls.

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