One of Lone's gunmen, Mushtaq Ahmed, was also killed and another injured when the assailants in police uniform opened fire during a rally to mark the 12th death anniversary of the former Mirwaiz of Kashmir, Maulvi Mohammad Farooq, father of senior Hurriyat leader Umar Farooq, at Idgah ground in old Srinagar city.
Seventy-year-old Lone was rushed to the Soura Medical Institute where he was declared "brought dead".
The assailants also lobbed a grenade which failed to explode, official sources said.
At least seven people were injured in the attack, which took place as the ceremony was about to end at 6.15 p.m.
Hurriyat Chairman Abdul Gani Bhat, who was present at the rally, said he was escorting Lone at the conclusion of the ceremony but missed him due to pressure of crowds.
Shortly thereafter, he said, he heard sound of gun shots and later realised that Lone had been shot at along with his gunmen. Some other persons were also injured in the shootout.
Lone's killing comes on the eve of Vajpayee's visit to the valley to take stock of the ground situation
including at the borders and ahead of October assembly elections in Jammu and Kashmir.
Lone's body was later brought to his Rawalpura residence where hundreds of people had assembled.
No one has so far claimed responsiblity for the attack.
Jammu and Kashmir Chief Minister Farooq Abdullah, condemning the killing, said it indicated that Pakistan would not allow those who want a peaceful resolution to the Kashmir issue to live.
Lone is survived by his wife, two sons and a daughter. His one son is married to the daughter of Pakistan-based JKLF leader Amanullah Khan.
Moderate Among Extremists
A founder Executive Committee member of the 23-party Hurriyat, Lone had been a critic of 'jehadi' and foreign mercenaries and had indicated desire for holding talks with the Centre for resolution of the Kashmir issue.
He, along with Mirwaiz Umar Farooq, recently held talks with leaders of Pakistan-occupied Kashmir (PoK) in Sharjah which created a controversy and led to some differences within the Hurriyat Conference. He was under attack from hardliners for his stand that violence was no solution to the Kashmir problem.
Incidentally, he returned to Kashmir only last weekend after a month-long tour of the US. Earlier on April one, Lone was manhandled by a Shiv Sena leader during a press conference in Jammu.
A man of conviction, Lone was never afriad to be a loner and virtually single-handedly conducted a mass awareness campaign over the Kashmir issue by holding dialogue in different parts of the country last year.
Born in 1932 in Haral village of Baramulla district, Lone did his B A and B Ed and later secured LLB from Aligarh Muslim University in 1967.
He was active in students' union and after leaving the university joined the Congress
in northern Kashmir. He also enrolled himself as an advocate of the High Court. He subsequently became
Director of Jammu and Kashmir State Cooperative bank, Land Development Bank and Senior Vice President of Jammu
and Kashmir Cooperative Union.
Lone was elected to the legislative assembly in 1967 and became a member of its privilege committee.
He was appointed a deputy minister in the ministry of G M Sadiq in 1970 and held the portfolios of irrigation, law and cooperative. He was re-elected to the assembly in 1972 with a thumping margin from Handwara and was elevated as a minister of state for tourism, health and education in the government headed by Syed Mir Qasim.
Lone resigned from the ministry in protest against corruption and joined Janata Party. He was one of the two party candidates who weathered the onslaught of National Conference and were elected to the assembly in 1977.
He then formed his own J & K People's Conference in 1977. This was the only separatist organisation registered with the Election Commission till 1996.
He joined the secessionist Hurriyat Conference at its inception in 1993. Lone claimed to be both anti-India and anti-Pakistan as he stood for the third option of an independent Kashmir, backed by Pakistan-based JKLF leader Amanullah Khan whose daughter married Lone's son two years back.