hina unveiled plans for sweeping changes in the structure and leadership of its central government today, opening what could be a politically divisive campaign to cleanse the bureaucracy of corrupt, aged and leftist officials said to be blocking national modernization plans.

The blueprint calls for halving the 98 governing bodies at the top of the bloated bureaucracy, reducing the number of policy-making vice premiers from 13 to 2 and slashing overall a third of their staffs, according to a report approved by the standing committee of the National People's Congress.

A tough, new anticorruption law allowing the death penalty for serious offenders was adopted by the lawmaking body as well as China's first mandatory retirement statute, which requires officials of ministerial rank to step down at age 65 and vice ministers at 60.

"The leading members are, step by step, to be revolutionized, younger, better educated and professionally more competent," according to the official New China News Agency, which reported the standing committee's decision after its meeting ended.

Although most details of the plan have been reported in recent weeks, their ratification by China's top lawmakers provides momentum for the housecleaning Vice Chairman Deng Xiaoping calls "another revolution" that is vital to the success of his political and economic reforms.

China is ruled by the Communist Party, but it is administered by a state government apparatus headed by the State Council, which implements the party's decisions. The same people who run the party generally run the government or entrust it to their allies.

Today's approval by the rubber-stamp parliament may broaden Deng's consensus for bureaucratic trimming, but it is not likely to clear away resistance from some entrenched cadres who are expected to muster all their political strength to hold onto their sinecures.

Nevertheless, the first swing of the ax appears to have landed cleanly with the parliament backing plans to merge nine agencies dealing with commerce, trade and energy into three new ministries that will reduce their staffs by a third of the old bodies and cut top officials from 117 to 27.

The three new agencies and a streamlined Ministry of Chemical Industry are to be headed by a new breed of Chinese official. The four ministers are in their fifties and early sixties and come equipped with strong professional credentials and administrative experience.

To make room for them, the standing committee approved proposals to "relieve" ministers in their late sixties and seventies who apparently were disqualified by age or misfeasance or political unacceptability to the pragmatic leaders now running the nation.

Among them are former commerce secretary Wang Lei, who was accused in 1980 of enjoying lavish banquets at a fancy Peking restaurant for a fraction of their cost. The outgoing minister of chemical industry, Sun Jingwen, is thought to be a member of the so-called petroleum faction of politicians who supported the grandiose economic programs of Deng's political opponents.

Other bureaucratic changes approved by the lawmakers include beefing up the State Economic Commission by giving it responsibility for four now-abolished commissions dealing with agriculture, capital construction, machine-building and energy.

Reforms revealed today are the first phase in what is slated to be a yearlong effort to trim central government posts by 17,000 jobs. The number of ministers and vice ministers for each ministry will be fixed at three or five instead of the more than 20 who often are assigned to one ministry now.

Age limits will be imposed "under normal conditions," the Chinese news agency reported. That apparently leaves room for maneuver for some of Deng's top lieutenants who exceed the ceiling now. For example, Vice Premier Wan Li, architect of China's new agricultural policies, is 67.

New anticorruption laws aimed at restoring the party's good name among a cynical population call for maximum penalties of death for officials convicted of taking or extorting bribes, illegally purchasing foreign exchange, speculating for large profit, selling narcotics or stealing and exporting cultural relics. Peking Claims Vietnamese Shelled Chinese Vessels Washington Post Foreign Service

PEKING, March 8--The simmering Sino-Vietnamese dispute flared up on the South China Sea last week when Vietnamese boats shelled Chinese fishing vessels, leaving six fishermen wounded and 18 missing, the official New China News Agency said tonight.

The incident, which is said to have occurred March 3, would be, if confirmed, one of the most serious military encounters at sea since the two nations fought a border war in 1979. It comes amid recent claims by both sides to offshore islands where there are believed to be rich offshore oil fields.

The Chinese Foreign Ministry lodged a strong protest with Hanoi today, demanding an immediate return of fishermen and their boats seized in the alleged attack, compensation and a halt to Vietnamese raids at sea and across the 90-mile common border.