China's sensitive northwest region that borders the Soviet Union has been shaken in recent months by communal fighting and ethnic group demands for greater rule, according to diplomatic and Chinese sources.

The recent trouble in Xinjiang Province constitutes China's most serious minority problem in years and has already prompted emergency inspection tours by Chinese Politburo members and top provincial leadership changes.

Xinjiang's stability is of great concern to Peking because of the province's location contiguous with four unfriendly neighbors--the Soviet Union, India, Mongolia and Afghanistan. It also is home for the Lop Nor nuclear test site and 250,000 Chinese border guards.

The region's strategic sensitivity is sharpened by what the Chinese claim to be constant Soviet radio broadcasts beamed into Xinjiang in several tongues urging the province's various minorities to resist Chinese domination.

Longstanding ethnic tension recently surfaced as a result of renewed demands for self-rule by the Uighurs (pronounced we-gurs), a Turkic people of Moslem faith who compose the largest minority in Xinjiang.

The Uighurs, who make up almost half of Xinjiang's 12 million people, ask for greater religious freedom and fiscal autonomy from Peking and for less control by Chinese, who are fewer in number but occupy the top posts in the party, government, military and police force.

Ethnic friction exploded into a series of violent incidents pitting Uighurs against Chinese in at least two Xinjiang cities, according to Chinese sources and reports in the Hong Kong communist magazine, Cheng Ming.

The first incident in April 1980 began after a Uighur man was killed by two Chinese in the eastern Xinjiang city of Aksu, according to Cheng Ming. The Uighurs retaliated by beating up several hundred Chinese, smashing Chinese homes and damaging a factory run by Chinese, the magazine said.

A few months later in the southern city of Kashi, a Chinese soldier driving a military truck struck and killed a Uighur pedestrian. When the court dominated by Uighurs convicted the driver and sentenced him to death, the predominantly Chinese police force refused to execute him and the local Army command threatened to mutiny if the sentence was carried out, Cheng Ming reported. Further trouble was averted when the sentence was commuted.

Another incident occurred in June in Kashi, which is 60 miles from the Soviet border. After weeks of fighting with Chinese, a band of 200 Uighurs tried to storm an Army base outside the city, according to a Chinese source. The attack was repulsed and the Uighur leaders arrested, said the source who lives in Xinjiang.

Trying to restore stability, Peking dispatched Politburo member Wang Zhen to Xinjiang twice in 1980. But Wang, who served as the province's first party secretary until the early 1950s, was unable to contain the violence and political fissures within the provincial party committee, according to diplomats.

The situation deteriorated so badly last month that Vice Chairman Deng Xiaoping, who is China's most powerful political leader, traveled the 1,500 miles from Peking to Xinjiang to help mediate political infighting between Chinese and Uighur members of the provincial ruling committee, according to diplomats.

Although publicly Chinese officials describe Deng's nine-day visit as a "routine general inspection," others say privately he confronted a revolt by Uighur provincial committee members against the Chinese ruling majority.

High-ranking Chinese officials have told diplomats that Deng ordered a reorganization of the provincial committee, which serves as Xinjiang's local ruling body. The diplomats were told that Xinjiang's first party secretary, Wang Feng, was recalled to Peking, although that report was later publicly denied.

The second party secretary, however, was replaced within recent months. The new official, Gu Jingsheng, was the deputy political commissar of the Canton military command. His military background is said to reflect Peking's interest in reestablishing order in Xinjiang.

In its September edition, Cheng Ming reported that Deng discovered an "unsteady situation" in Xinjiang. The magazine said that Uighur dissidents had planned a province-wide uprising against Chinese rule, following the slogan "We want self-rule and don't want to be dominated."

Xinjiang, a vast and arid outback in the northwest corner of China, is one of five so-called autonomous provinces with large concentrations of minorities. These regions were set up by the Communist Party as places where China's ethnic groups could enjoy some degree of freedom to practice their religion, maintain their traditions and teach their languages.

Although China has more than 50 different minority strains, they make up only 6 percent of the nation's 1 billion people. China's vast majority are known as Han Chinese, named for the Han Dynasty of 2,000 years ago that laid the foundation of the Chinese empire.

Despite their high-minded minorities policy, communist leaders have long encouraged, and sometimes forced, migrations of Han Chinese settlers to the autonomous regions to dilute ethnic influence and help assure central control along China's troubled borders.

This was especially true in Xinjiang, where Uighurs and other Moslem minorities have longstanding ties with Turkic people in the Soviet Union. Part of the province was ruled by a Soviet-sponsored semi-autonomous regime before the communist takeover in 1949.

Since 1949, 5 million Han Chinese have been brought to Xinjiang from eastern China to help assimilate the Uighurs, Kazakhs, Tatars and other minorities who are among the most rebellious in China.

The integration effort began with the founding of the commune in 1958 and greatly intensified during the Cultural Revolution (1966 to 1976), when the Arabic script was outlawed in favor of the Latin alphabet, mosques were closed, Moslem classics burned and traditional songs replaced by radical leftist dogma.

This clash of cultures resulted in fierce fighting in 1967 when thousands of Red Guards went to Xinjiang and criticized the religious practices of the proud Uighurs as "feudal."

Since the Cultural Revolution, Peking has taken pains to ensure ethnic rights and elevate minority group members to leadership positions. In Xinjiang, a kind of affirmative action program has been started at the provincial university to guarantee that 60 percent of new students are from ethnic backgrounds.

Cadres of Uighur background have been given special priority for enrollment in party schools and training institutes to raise their educational level, and in recent local elections, Uighurs and Kazakhs have won a majority of the seats.