The United Nations has condemned the mass abduction of students at the Government Science School at Kankara, Kastina State.
The organisation expressed its concern in a statement by the Spokesperson for the Secretary-General, Stéphane Dujarric, on Monday.
Gunmen on motorcycles stormed the Government Science School at Kankara late on Friday. They engaged security forces in a fierce gunbattle, forcing hundreds of students to flee and hide in surrounding bushes and forest.
Katsina State Governor Aminu Masari, who visited the school on Saturday, said soldiers were working to locate and free the hostages.
On Sunday, the governor noted that 333 students were still missing.
It read, "The Secretary-General strongly condemns the 11 December attack on a secondary school in Katsina State, Nigeria, and the reported abduction of hundreds of boys by suspected armed bandits.
"The Secretary-General calls for the immediate and unconditional release of the abducted children and their safe return to their families. He reiterates that attacks on schools and other educational facilities constitute a grave violation of human rights. He urges the Nigerian authorities to bring those responsible for this act to justice.
"The Secretary-General reaffirms the solidarity and support of the United Nations to the government and people of Nigeria in their fight against terrorism, violent extremism, and organised crime."