The 17-year-old laureate from Pakistan, who was shot in the head by a Taliban gunman, said young people the world over face problems.
"As (he) was from Mexico, so there are problems in Mexico," she said after meeting Norwegian Prime Minister Erna Solberg. "It is really important that children raise their voices."
Oslo police said the flag-waving 21-year-old, who has applied for political asylum in Norway, was fined $2,100 for disturbing the peace and sent back to an asylum center.
Malala told reporters she was not afraid when the intruder stepped out in front of her and co-winner Kailash Satyarthi as they were holding up their award certificates and medals in front of hundreds of guests.
"There was nothing to be scared of," she said.
The man was quickly whisked away by a security guard but police were unable to explain how he had managed to enter Oslo City Hall without an invitation amid tight security in the city.
The broadcaster reported that Cortes Salas had wished to draw attention to the disappearance in Mexico in September of 43 demonstrating students. Prosecutors there say local police probably turned the students over to gang members, who may have killed them and burned their bodies.
In Malala's case, they were killing female students, but in Mexico they kill male students too, Cortes Salas said.
"The situation is really awful," he said. "I'm worried about myself and my own security."
Malala, the youngest ever Nobel Prize winner, shared the $1.1 million award with the 60-year-old Kailash Satyarthi for helping protect children from slavery, extremism and forced labor, and advance their education.
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