ABUJA, July 25 (Reuters) - Armed bandits in Nigeria have seized a negotiator who had been sent to pay ransom money to secure the release of 136 students kidnapped two months ago from an Islamic school in the north of the African nation, the school and parents said. Abubakar Alhassan, director of the Islamic school, said the school and parents have been negotiating with the kidnappers who demanded 30 million naira ($72,993) to release the students from the school in Nigeria"s Niger state. Alhassan said the school had contributed to a ransom and some parents sold property to raise cash but they said the negotiator, a 60-year-old man from the community, was taken because kidnappers said the ransom he brought was short. Armed groups have been blamed for a series of raids on schools and universities in northern Nigeria in recent months, abducting more than 1,000 students for ransom since December. The government has said it would not pay any ransom. President Muhammadu Buhari has ordered security forces to search for the students. read more "We sold most of our properties and used our savings to see that our children are returned. Unfortunately after all the effort, they said that we did not bring the money as they required," said Ibrahim Salihu, father of two of the children abducted by the school in Niger state. "We are now left with nothing and our children are still held captive," he said. The police did not respond to a request for comment. Kidnappings in Nigeria began with abductions by jihadist group Boko Haram and its offshoot Islamic State West Africa Province. Now criminal gangs have used the tactic. Kidnappers released 28 students seized from another school on Sunday, but kept hold of 81 other students. read more