A senior official in Afghanistan's ruling Taliban regime said talks "went well" today between Indian negotiators and the hijackers holding 155 hostages aboard a grounded Indian Airlines jet in Afghanistan.

The hijackers continued to demand the release of 36 Kashmiri insurgents imprisoned in India, while Indian authorities denied they had agreed to free some of the detainees.

After three days of negotiations, "We are optimistic," Wakil Ahmed Muttawakil, the Taliban foreign minister, told reporters late tonight in Kandahar, the city in southern Afghanistan where the plane is grounded. Earlier today, authorities in New Delhi said the talks came to an impasse and were "delicately" poised to resume only after Afghan officials increased security around the plane.

Heavily armed Taliban commandos have surrounded the Airbus A300 on the runway. Taliban authorities have threatened to storm the plane if any hostages are harmed, and they have said they will attempt to force the jet to leave Afghanistan if a solution is not reached soon.

Tonight, Taliban sources in Pakistan said the hijackers had been given until Friday to resolve the situation or leave Afghanistan. It was not clear whether they would use force to evict the plane.

Some diplomats and Taliban officials in Kandahar said Wednesday that the negotiations, conducted by radio, walkie-talkie and pieces of paper dropped from the Indian jet, had moved toward a discussion of how many insurgents would be released in exchange for the passengers and crew.

"They are still negotiating on the numbers of prisoners," said Muttawakil, who has spent hours at the airport each day.

But Raminder Singh Jassal, a spokesman for the Ministry of External Affairs in New Delhi, flatly denied that India had made a deal to release any insurgents. "There is no such agreement," he said. India is under pressure from the hostages' relatives to release some prisoners, but its military leaders strongly oppose such a concession.

As the saga entered its seventh day, the hijackers reportedly came under increasing pressure from Taliban leaders and other radical Islamic groups in the region to seek a peaceful solution. Top Muslim leaders in India today offered to travel to Kandahar to help end the stalemate.

On Wednesday, the hijackers dropped two demands -- for $200 million in ransom and the exhumation and return of one slain insurgent's body -- after Islamic leaders protested that the requests were "un-Islamic."

Today the hijackers allowed a cancer-stricken hostage to leave the plane for medical treatment and then return. Since seizing the plane last Friday, they have freed 27 passengers and permitted Indian doctors on board to treat a number of ailing people. However, they also stabbed to death one Indian man who defied their instructions not to look at them.

Conditions aboard the stranded jet were described today as reasonably comfortable. Indian doctors and engineers allowed on board said passengers were permitted to move about the cabin, and were passing the time by playing cards and listening to music. The Taliban has provided the hostages with food and basic supplies each day.

[Early Friday, however, as temperatures dropped below freezing, the engines on the plane inexplicably shut down, cutting the heat to those on board, the Associated Press reported. In New Delhi, Indian Foreign Minister Jaswant Singh said he would leave for Kandahar to assist in negotiations.]

The five or six hijackers, reportedly including several Pakistanis, a Nepali and an Afghan, appear to be part of a movement by violent Islamic separatists to free Kashmir from Indian military and civilian control. Kashmir is a Himalayan border region divided between India and Pakistan, and claimed by both countries.

The hijackers' chief demand remains the release of Maulana Masood Azhar, a Kashmiri rebel leader and Islamic scholar who has been jailed since 1994 near the Kashmiri city of Jammu. Azhar has been quoted from prison as saying he does not want to be freed "at the cost of innocent lives."

Azhar's organization, Harkat ul-Mujaheddin, has been declared a foreign terrorist group by the United States. On Wednesday, group officials claimed responsibility for attacking a fortified police compound near the Indian Kashmiri city of Srinagar, which left at least seven people dead.

Meanwhile, the jet remained surrounded by teams of heavily armed commandos who camped on the tarmac in shifts, lighting fires to keep warm in the sub-freezing Afghan winter nights. But Muttawakil said that the commandos were being deployed only for "security" purposes and that his government is "not planning any operation" against the hijackers.

In the past 72 hours, the Taliban, whose fundamentalist Islamic regime is an international pariah, have assumed the role of mediator between the Indians and the hijackers, gaining them respect and gratitude from India, a predominantly Hindu nation. But Taliban officials have grown increasingly impatient with both sides, saying it is up to them to solve the problem.

"Our demand for both sides is not to waste time, and find a political solution," Muttawakil said Wednesday. If India does not meet some of the hijackers' conditions, he said, "our next step will be to ask the hijackers to leave Afghanistan, or we will force them to leave."

Special correspondent Debdeep Chakraborty in New Delhi contributed to this report.