In the highest-level purge in two years, China's current leaders have fired the mayor of Peking, according to diplomatic sources in Peking.

The sources, reached by telephone, said Chinese office workers and a group of German journalists visiting the official People's Daily had been told that the ousted mayor, Wu Teh, 68, would undertake "study sessions" outside the capital. They indicated he would retain his seat on the Communist Party Politburo, the top 23 leaders in the country, but would no longer have much real political power.

Although the report is yet to be officially confirmed, the sources said a veteran party official named Lin Hu-chia had been selected to replace Wu as mayor. Just this past summer, Lin was named mayor of Tientsin, China's third-largest city 100 miles southeast of Peking, in the purge of another official disliked by the government and army veterans now running the country.

Wu has been the top party official in the administration of China's capital city since 1972, but has been under sporadic attack since the 1976 purge of a dogmatic Politburo faction led by the late chairman Mao Tse-tung's wife, Chiang Ching. Wu appeared to have cooperated with the faction before its demise. He has been criticized severely in wall posters during the last year for allegedly suppressing an unprecedented mass demonstration in Peking's Tienanmen Square on April 5, 1976.

The demonstrators, in what appeared to be a rare outpouring of spontaneous protest in China, had objected to reported attempts by Chiang Ching to discourage mourning for the late, popular premier, Chou En-lai.

Two days after the demonstration, Vice Premier Teng Hsiao-ping, the intellectual leader of a group of veteran officials favoring pragmatic methods to save the economy and raise living standards, was removed from all his official posts. After Mao's death in September 1976 and the purge of his wife and her allies the following month, Teng's friends began to organize his political comeback, but Wu apparently resisted.He called publicly for continued criticism of Teng after everyone else had dropped the idea.

Wu retained his job as mayor and his seat on the Politiburo, apparently through a compromise worked out by Mao's successor, Chairman Hua Kuo-feng, before the 11th party congress in August 1977. Hua apparently wanted to keep Wu and others like him on the Politburo to give an impression of party unity and to balance the renewed influence of the rehabilitated Teng and his cohorts.

Teng, 74, apparently has found a way to cooperate with his much younger superior, Hua, 57, but has continued to unseat other party leaders who have not suited him. Wu is the highest official to lose out in this campaign led by Teng to weed out remaining officials who might have a soft spot for Chiang Ching and a history of supporting student activism and forced retirements of party veterans.

The fall of Wu reflects Teng's pervasive influence and leaves some doubts about the extent of Hua's ability to influence events, despite his hold on the top positions in the party, government and army. But Hua does not appear to have any significant differences with Teng on the need to modernize the economy and discipline uncooperative bureaucrats.

The removal of Wu may indicate that Hua has become so confident of his own position, bolstered by a recent successful tour of Eastern Europe, that he no longer sees the need to protect troublesome allies like WU.

During a career spanning 12 years at or the near the top to the Peking administration, Wu has apparently made himself quite unpopular. Wall posters have criticized him for supporting student criticism of teachers and veteran officials, and slapping opponents in jail. One posted cartoon showed him in the form of a lead-bottomed doll that falls over when hit but always bounces back.

Wu may now fall into the political limbo that has embraced Saifudin, the alternate Politburo member who was allowed to retain his central party seats after being removed as Sinkiang regional chief in January. Saifudin still makes ceremonial appearances and Wu may continue to appear as a Politburo member and as vice chairman of the National People's Congress, the rubber-stamp parliament.

Other provincial leaders thought to be in disfavor with Teng, such as Jen Jung of Tibet and Li Jui-shan of Shensi, may find their positions deteriorating further following Wu's ouster, analysts here and in Peking say.