GUWAHATI, July 17: In another major breakthrough a police team arrested a top ULFA militant suspected to be the linkman with Pakistan's Inter Services Intelligence at Vellore in Tamil Nadu. Sources said that the police team acting on specific information conducted a raid at Vellore and arrested the top ULFA militant Hasan Ali who happens to be the member of the ULFA's central committee. He was also the chief of the Chaur Development Committee of the outfit and was mainly doing liaison work among immigrant population to which ULFA has of late started using as their hideouts in the state. He is suspected to have been in Tamil Nadu on special mission to explore the possibility of nexus with the LTTE militants. Sources indicated that his arrest was a major setback to the outfit's future plan to spread its tentacle and link in other parts of the country. The police sources said that Hassan Ali among a few Muslim members of the ULFA's central committee had also visited Bangladesh several times and is believed to have been maintaining link with the ISI agents. He was produced in the court at Vellore on Sunday and was likely flown to Guwahati on Monday for further interrogation, the police sources said. Ali had gone Vellore about 10 days before and was staying in a rented cottage. The police team led by Dhubri district police in co-ordination with Tamil Nadu police picked up Ali on Sunday. Senior police officers when contacted were quite tight-lipped about the arrest though they confirmed the report on strict condition of anonymity.