The former prime minister said he had approached the British government to discuss the possibility of military assistance. Asked if he anticipated a positive response, he said: "I think people will want to help, yes."
Stressing the urgency of locating the kidnapped girls, Brown told the Guardian: "The international community must do something to protect these girls. We could provide military help to the Nigerians to track down the whereabouts of the girls before they're dispersed throughout Africa – like air support, for example, if that was thought necessary."
Brown will meet the Nigerian president, Goodluck Jonathan, in Abuja next week to discuss the abduction. He declined to say whether he planned to travel to the remote and dangerous Borno province in the north of the country, from which the girls were kidnapped on 14 April.
Amid widespread criticism in Nigeria of the government's failure to locate the girls, Brown said his intention was to support Jonathan. "I'm not prepared to criticise the Nigerian government. We're dealing with a group of terrorists who have kidnapped children … The sensible way of dealing with this is to help the Nigerian government to deal with a problem in their own country that is very substantial."
The girls, aged between 16 and 18, were snatched in the middle of the night from dormitories at a school in Chibok. Parents and local activists put the number at 230, of whom more than 40 managed to escape from trucks transporting them into the forest. The rest are still missing.
The provincial government in Borno initially said 129 girls were abducted, of whom 52 escaped. The violent jihadi organisation Boko Haram is believed to be responsible.
Since the abduction, there have been conflicting reports of the girls' fate, including claims that they have been trafficked across the border into Cameroon.
"Two hundred girls have been abducted, kidnapped, taken into a forest area, and their parents don't know whether they are about to be murdered, or used as sex slaves, or about to be trafficked into other countries," said Brown.
Relatives told the Guardian this week that the girls had been forced into marriage. "We have heard from members of the forest community where they took the girls. They said there had been mass marriages and the girls are being shared out as wives among the Boko Haram militants," said Samson Dawah, a retired teacher whose niece Saratu was among those kidnapped.
Nigerian armed forces have been searching the 60,000-sq-km Sambisa forest, but say their efforts are being hampered by tip-offs to the militants.
The incident was not isolated, said Brown: "For years now girls in northern Nigeria have been prevented from going to school by terrorists and by the failure to protect them in safety. We've seen hundreds of girls and boys who've been murdered over recent years."
In his capacity as United Nations special envoy on education, he said, he would be urging the Nigerian government to take measures, with international support, to make schools more accessible and safer.
More than 10 million children in Nigeria did not attend school, Brown said. As well as widespread barriers to children's attendance – including child labour, child marriage, child trafficking and discrimination against girls – he added that in northern Nigeria there was "a persistent campaign to deprive children of the opportunity to go to school as part of the wider aims of Boko Haram".
The jihadi group was responsible for "probably 5,000 deaths" in northern Nigeria in the past five years, "including a very large number of pupils, because a target of Boko Haram is to go into schools to bomb and to burn them". Boko Haram means "western education is a sin".
Children, said Brown, should "not be afraid of having to go to school in the face of terrorism". He added that schools should be protected places, like hospitals, under the auspices of the UN or Red Cross.
Amnesty International believes about 1,500 people have been killed by the group in the past year. On the same day as the Chibok kidnappings, 70 died in a bombing in Abuja.
Several hundred people marched through Abuja on Wednesday, many accusing the government of laxity in finding the girls.
Pogo Bitrus, the leader of the Chibok elders forum, told AFP it was "unbelievable" that the military had not tracked down the girls.
Brown attacked the international media for being slow to report the mass abduction. "I'm absolutely shocked at the failure of the international media to take up this issue – including, for several days, the Guardian." The Guardian first reported the story on 15 April.
Guardian
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