China's leaders are stepping up efforts to defend their economic reforms and fight government corruption that could undermine the changes and the credibility of top leader Deng Xiaoping.

Top-level Chinese officials completed an unprecedented public denunciation of official wrongdoing last week during a conference of more than 8,000 leaders from the Communist Party, government and Army. During the past few days, their speeches have been appearing, one at a time, in the government media.

Some diplomats here say the size, scope and seriousness of the meetings were such that the reform group led by Deng now must produce examples of fairly high-level economic crimes and deliver the appropriate punishment or they will lose considerable credibility.

Although each of the officials who spoke on the subject was careful to say that "only a small number" of officials and party members had engaged in illegal business activities, fraud and swindling, or had accepted bribes, their remarks indicated to diplomats that economic crime has reached new levels of seriousness.

This was evident in a speech delivered last week and broadcast in part on national television tonight in which Yang Shangkun, vice chairman of the Communist Party's powerful Central Military Commission, said that while "only a small number" of military men had engaged in economic crime, it was a "serious" problem.

A Chinese military publication had confirmed last summer that the Chinese Navy played a role in illegally transporting thousands of imported motor vehicles and other goods to Hainan Island, the biggest profiteering scandal to be disclosed since the nation began its open-door policy toward trade and investment six years ago.

The officials who organized the meetings seem to be aware that until now many people have accused them of "swatting at flies while ignoring the tigers."

Deng was not present at the meetings, but measures announced during the meetings to counter corruption bore the marks of his style. These moves are apparently designed to assert control over an issue that is in danger of being used by critics against his reformist group.

"Deng is making a gesture to the critics without abandoning the basic course," said a diplomat, who requested anonymity.

But other diplomats detected a tone of defensiveness on the part of some reformers. Should the reformers fail to cope with the corruption problem, the possibility of a power struggle occurring once the influential Deng passes from the scene is greatly increased, diplomats said. They did not see evidence of a power struggle or factional battle in the meetings last week.

The conservatives do not have the strength to make a bid for power, they said. Deng and his allies ousted numerous critics and reluctant reformers from the party's Central Committee at a major party conference last September.

The directives from Peking so far have conveyed the impression to the provinces that officials would get their wrists slapped for corruption, said one diplomat here. "Now they've got to send some directives calling for examples of more severe punishment," he added.

Another diplomat quoted a widely known Chinese proverb about Chinese leaders punishing an individual or small group to set an example for the larger group. "They're going to have to kill a chicken to scare the monkeys," he said.

The lineup of speechmakers at the two meetings last week included Party General Secretary Hu Yaobang, Premier Zhao Ziyang, Vice Premier Tian Jiyun, Wang Zhaoguo, director of the general office of the party's Central Committee, and Hu Qili, a rising Politburo member and permanent secretary of the Secretariat.

None of these officials is considered to have doubts about the reforms, or at least doubts about the way they are being implemented.

In a speech published today in the official People's Daily, considered by some diplomats to be the most important speech of the meetings, Wang mentioned six types of problems to be addressed, including extravagant luxury imports and gift-giving, and officials who seek benefits only for their children, relatives and work units, and not for the country as a whole.

Wang urged people to report corruption cases to the party Central Committee even when they involved officials at high levels.

"But the problem is that nobody is clean in this society," said a diplomat. "If they themselves are clean, then their kids aren't. It's endemic, " he said. "The higher you get, the bigger it is."

This diplomat, who said he had no evidence to support his claim, asserted that the reformists might also select people who are their political enemies when they make examples of government corruption.

Not all diplomats agreed about the significance of the meetings. Some consider what has just occurred to be little more than a propaganda exercise designed to appease those who are angry about reports of corruption at high levels. Among the discontented are some of the country's urban workers and an undetermined number of university students who feel they have failed to benefit so far from the reforms.

Some diplomats suspect that even if it tries, the Communist Party will not be capable of disciplining itself. In the past, punishment of corrupt officials rarely has reached above the middle levels of the party, government and Army. An exception was the Hainan case, where several leading officials and cadres were removed from their jobs on the island.

In early December, however, some signs of a new seriousness emerged. A court sentenced 23 party and government cadres to 10 years in prison for fraud, bribery, and tax evasion, and the convicted were exposed to unusual television coverage. But the usual pattern has been one of reprimanding guilty cadres, having them go through self-criticism and then demoting them or even keeping them in place while not even expelling them from the party.