However, according to sources, he was brought from Nepal from the Kishtwar police on August 9.
He also reportedly had close links with the former Pakistani diplomat in Nepal though the police didn't reveal the name of the country of the diplomat and also didn't reveal his identity.
Mehraj-ud-din alias Javed Dan was also closely associated with Syed Salahuddin, one of the most wanted terrorists heading the United Jihad Council from the Pakistan Occupied Kashmir (POK). According to the police he was actively involved in the activities of the Dawood Abrahim gang. Both figure in the intelligence agencies' list of the 20 most wanted men.
"Mehraj-ud-din, resident of Sopore, Kashmir, was actively involved in terrorist activities since 1989 and was arrested by the Kisthwar police. He had close links with a foreign diplomat based in Nepal," said inspector general of police (IGP), Jammu, Dilbgah Singh told the media on Thursday.
Meharj-ud-din was the first arrested in 1987 when he was involved in separatist activities and sent to jail. UIC chairman Syed Salahuddin was also arrested in the same year after he had unsuccessfully contested the controversial elections in 1987 from the Amirakadal in the heart of Srinagar.
"Mehraj-ud-din came in contact with Salahuddin when they were lodged in Kot Bhalwal jail," said the IGP.
Both were released in 1989 and he along with Salahuddin was amongst the first few people to cross over to the POK to get arms training.
The IGP said that though the terrorists had admitted his involvement in the hijacking the police had credible information in this regard and are working on it.
The Indian Airlines plane was hijacked on Dec 24, 1999 after it had taken off from Nepal and had been taken to Kandahar in Afghanistan. Three top terrorists including Masood Azhar and Omar Sayeed Sheikh were released for the safe return of the passengers.
Nepal had emerged as the crucial link in the case.
Even though the police didn't name the Nepal based foreign diplomat, but police sources said that Salahuddin had developed close links with the first Mohammad Asif Cheema, the first secretary in the Pakistani embassy there. Sources said Cheema had provided logistics to the hijackers.
Cheema was arrested in 2000 from Kathmandu and 16 kg of RDX was recovered from him.
"Meharj-ud-din had admitted having knowledge of the 1996 Lajpat Nagar blast in Delhi," said Singh. 13 people were killed in the blast.
Police said that Meharj-ud-din had married a Hindu girl in Nepal and had changed his identity several times and acquired different passports. The police had recovered different identity cards from him.
"As per our information, at one point even separatist leader Sayeed Ali Shah Geelani had helped him get a visa for Pakistan," said Singh.
According to the police, Meharj-ud-din was planning to go to Kashmir via the Sinthan pass which connects the valley with the Kishtwar district of Jammu region.