The two nations have billed the bus service between Srinagar and Muzaffarabad as one of the biggest confidence-building measures between the two South Asian neighbours.
But in a joint statement issued on Wednesday, four obscure groups fighting Indian rule in the Himalayan state said they were opposed to the bus link between the two principal towns of the divided state, on the grounds that it would harm the Kashmiri freedom struggle.
Pakistan and India have fought two of their three wars over the dispute on Kashmir since their independence from Britain in 1947.
The decision to start the service was taken on 16 February during Indian Foreign Minister K Natwar Singh's two-day visit to Pakistan.
Indian Prime Minister Manmohan Singh will flag off the inaugural bus on 7 April at a grand function at Srinagar, the summer capital of Indian-administered-Kashmir.
Politicians and celebrities from across India and abroad have been invited to the ceremony. Among them is Sonia Gandhi, the chairwoman of India's ruling United Progressive Alliance.
Army engineers have carried out
extensive repairs to the old road
But the fighting groups have called for a shutdown on 7 April in protest the service.
"The people of Kashmir have been fighting jihad to liberate their land and seek Islamic salvation, but the bus is part of a deep-rooted conspiracy to harm their just struggle and intended to strengthen the Indian yoke," said a statement faxed to journalists in Srinagar on Wednesday.
Groups alleged to be fronts
The groups opposed to the bus are Al-Nasirin, Save Kashmir Movement, Al-Aarifin and Farzandan-e-Millat.
Indian officials in Kashmir said all the four are the fronts of well-known pan-Islamic groups such as Lashkar-e-Tayaba, Hizb al-Mujahidin and Jaish-e-Muhammad. These groups have strongly denied similar charges in the past.
The joint statement claimed an extraordinary meeting of the "supreme commanders" of the groups was held in Srinagar to discuss the bus service and its implications on the Kashmiri freedom struggle.
The bus service is being touted as
a major confidence-building step
It also criticised the moderate Kashmiri separatist leadership for extending support to the bus service.
Dream of many
The statement accused Pakistan's president, General Pervez Musharraf of "constantly working against Islamic forces in Pakistan".
Nonetheless, the chief minister of Indian-administered-Kashmir, Mufti Muhammad Sayid, said on Wednesday that the bus would realise the dream of many Kashmiri generations.
"It is a great stride and the biggest confidence-building measure since 1947," he said, adding that this would have "a healing effect for a people bruised by long turmoil and uncertainty in Kashmir."
Islamic groups say bus links will
dilute the separatist cause
The civil administration, army, police and other government agencies are heavily involved in making arrangements to ensure that the inaugural Srinagar-Muzaffarabad bus trip goes off without a hitch.
Discounting any security threat, India's army chief Gen JJ Singh said all necessary safeguards had been taken. "The army, in conjunction with the state government and police, have taken requisite measures to prevent any kind of security threat," he said.