Former president Nikolai Podgorny, a major Kremlin figure for more than a decade until his disgrace in 1977, died yesterday after a long illness, a Soviet spokesman said tonight. He was 79.

The portly, gray-haired Ukrainian, who served as head of state from 1965 to 1977, traveled the world as representative of the ruling troika, the triumvirate that also included prime minister Alexei Kosygin and party leader Leonid Brezhnev.

Unlike Kosygin and Brezhnev, who were given state funerals and buried in Red Square, Podgorny's remains will be laid to rest Friday at the Novodyevichi Cemetery on the banks of the Moscow River.

There has been no official statement so far about the death of Podgorny. The government news agency Tass today announced the death of Tikhon Kiselyov, 65, an alternate member of the ruling Politburo and Communist Party leader of Byelorussia.

Kiselyov's death creates yet another opening in the ruling body following the departures of Brezhnev, Mikhail Suslov and Andrei Kirilenko last year.

The vacancies are seen here as providing the new Soviet leader, Yuri Andropov, with the opportunity to bring younger persons into the Politburo at the next meeting of the Central Committee, to be held either in March or early April.

Podgorny, who owed his political rise to Nikita Khrushchev, was dismissed from the Politburo in 1977, apparently after a confrontation with Brezhnev. It is said that he had refused to step aside gracefully to let Brezhnev take the presidency.

In the dark world of Kremlin politics, Podgorny was unceremoniously expelled from the Politburo on May 24, 1977. The unexpected exit was dramatized by the fact that Podgorny came to the fateful Politburo session in a luxurious Zil limousine, the prerogative of all top leaders, and was taken home afterward in a regular Volga sedan.

In his 12 years as head of state, however, Podgorny had left a mark on that largely ceremonial post. As a member of the Politburo since 1960 and the titular head of state, he managed to establish himself as member of the inner leadership and frequently conducted full-scale negotiations with foreign leaders.

Shortly before his ouster, he led a 120-member Soviet delegation on an extensive tour of African states, paving the way for a deeper Soviet involvement in the southern part of the continent.

He had also undertaken a series of delicate missions to the Middle East, signing the ill-fated Soviet-Egyptian treaty in Cairo in 1971 and a similar pact with Somalia in 1974. In 1967, he became the first Communist chief of state to be received by a pope, calling on Paul VI at the Vatican during an official visit to Italy.

Podgorny bore a close resemblance in appearance and accent to Khrushchev. Podgorny traveled widely at home and abroad and acquired considerable strength in the party--establishing himself as one of the three top leaders alongside the more preeminent Brezhnev and Kosygin.

Podgorny's roots were unmistakably proletarian. He was born into the family of a foundryman in the Ukrainian town of Karlovka, near Poltava, on Feb. 18, 1903. At age 15, he went to work in a machine shop and joined the Young Communist League, soon to become an official in the local branch. Later he was sent to study at a technological institute of the food industry in Kiev.

In the 1930s he worked as an engineer at refineries in the Ukrainian sugar beet belt, joined the Communist Party and made his career in the food processing industry as deputy minister in the Ukraine and later as head of a food industry institute in Moscow.

His first significant political position was as Ukrainian representative to the Soviet goverment in Moscow, the post he was given in 1946. His real rise in the party hierarchy came in 1950, when he was made party secretary of the industrial Kharkov region in the Ukraine. He moved to Kiev in 1953 as second party secretary and four years later became the Ukrainian Communist leader.

It was as the Ukrainian leader that he gained admission to the inner ruling circle when he became an alternate member of the Politburo in 1958. Two years later he was made a full member. Khrushchev brought him to Moscow in 1963 and made him a national secretary of the party.

From then until 1977, Podgorny was at the center of Soviet power. He was made head of state, or chairman of the Presidium of the Supreme Soviet, in 1965.

After his ouster, Podgorny lived here in retirement and was occasionally seen attending ceremonial meetings as part of a crowd of officials rather than on the dais as was the custom when he was in power.

The decision to bury him at the Novodyevichi Cemetery, where Khrushchev is buried, suggests that Podgorny has not been fully rehabilitated.