Indian officials flew to Afghanistan today and opened negotiations for release of at least 155 passengers and crew members held for the fourth day aboard a hijacked Indian Airlines jetliner in conditions described as increasingly desperate.

The 52-member Indian team started work on a nerve-racking day in which the hijackers said they would begin killing passengers unless the government in New Delhi releases Maulana Masood Azhar, a Pakistani militant jailed in India in 1994 for his role in the violent struggle to separate the predominantly Muslim state of Kashmir from Indian rule.

Although several deadlines elapsed with no reports of anyone being killed, the threat was taken seriously by the Indian negotiators and Afghan authorities in charge at the Kandahar airfield in southern Afghanistan, where the Airbus A300 has sat since early Saturday. One passenger was killed Friday, soon after the plane was seized en route from Katmandu, Nepal, to New Delhi at the start of a journey in which it landed at and left airports in India, Pakistan and the United Arab Emirates before settling in Kandahar.

The Taliban government, which controls 90 percent of Afghanistan, responded to the death threats by encircling the plane with troops and telling the hijackers that Afghan forces would storm the aircraft if anyone was harmed. At the same time, India announced the dispatch of its negotiating team--doctors, diplomats and aviation experts--apparently also helping to dissuade the hijackers from carrying out their threat.

In Washington, the State Department condemned the hijacking "in the strongest terms," calling it an "inhuman" terrorist act and voicing encouragement for the Indian negotiating team. Indian officials said the team has no set timetable, but is operating under a broad mandate to secure release of the passengers, almost all of whom are Indian nationals.

"Our primacy is the safe return of the passengers and the crew," said Pramod Mahajan, India's parliamentary affairs minister. "Let us have the last victory by bringing them back."

But conditions were said to be deteriorating aboard the aircraft as it sat on the tarmac--doors shut, window shades drawn and engines running. The hijackers refused another request to allow women and children to leave the plane.

"It is very bad," Rehmatullah Aga, a Taliban spokesman in Kandahar, told the Associated Press. "The situation for the passengers is getting worse. They are tired and tense, and the hijackers are becoming agitated." Aga said the pilot pleaded, "Please get involved," in a radio conversation with the control tower, apparently addressing foreign governments and the United Nations.

A Taliban soldier who delivered rice to the hostages described the odor inside as overwhelming. "It smells like people have been sick," added Mohammed Khiber, an Afghan civil aviation spokesman.

Peter Iseli, a Red Cross official at the airport, said a doctor among the captive passengers has been taking care of those in need of treatment. "We are sending in basic medicines that you would expect in a situation like this, medicines for muscular pain because people have been sitting for so long, for headaches, nausea and stress," he told the Associated Press.

In India, fresh violence in Kashmir and growing anger among relatives of the passengers and crew on the hijacked jet contributed to what one official described as "a national crisis."

Militants in Kashmir launched attacks on police facilities in apparent sympathy with the hijackers. After the attacks, callers claiming to be members of Azhar's group, the Harkat ul-Mujaheddin, phoned local journalists and claimed responsibility.

Azhar, 45, was detained in the southern Kashmir Valley under an Indian anti-terrorist law and has been imprisoned ever since. He is being held in a jail near Jammu, in the town of Kot Balwal. He is known as a top fund-raiser and motivational speaker for the insurgent group, according to Kashmiri journalists and other informed sources. His followers have conducted several attempts over the years to free him by kidnappings, one of which ended in the murder of one Western tourist and the disappearance of three others when the Indian government refused to negotiate.

In New Delhi, relatives of those aboard the captured jet fought with riot police at the government's crisis management center and began a sit-in near the home of Prime Minister Atal Bihari Vajpayee. At a separate meeting on the hijacking, they demanded that Azhar be released so their relatives could also be freed--a step anti-terrorism experts and those involved in the struggle over Kashmir caution against lest it encourage terrorism.

"Sixty-seven hours have passed and the passengers are almost dead. What more can the terrorists do before the government decides to take any action?" said Anil Kumar, brother of one passenger, the Reuters news agency reported.

The plane had 178 passengers and 11 crew members on its manifest when it left Katmandu, although it is unclear whether the five hijackers were listed. Twenty-seven passengers were released during the stopover Friday night in Dubai and the body of a 28th was turned over to United Arab Emirates authorities there. Another passenger, said to suffer from diabetes, was released Sunday in Kandahar.

Correspondent Pamela Constable and special correspondent Debdeep Chakraborty in New Delhi contributed to this report.

CAPTION: A Taliban security official receives a paper on which hijackers wrote demands as the plane remained at the airport in Khandahar. The hijackers are seeking release of a Pakistani militant jailed in India.

CAPTION: Relatives of passengers on the hijacked plane protest at Indian prime minister's New Delhi residence.