MOSCOW, DEC. 2 -- President Mikhail Gorbachev today conceded one of the main demands of Communist Party hard-liners by firing his interior minister and putting a former KGB general and a top military commander in charge of law and order.

The official Soviet news agency Tass reported the replacement of Interior Minister Vadim Bakatin, who has been sharply criticized by conservatives for failing to put a stop to ethnic disorders, in a terse four-line communique. It said he was being replaced by Boris Pugo, 53, the head of the Communist Party's control commission who earlier served as head of KGB security police in the Baltic republic of Latvia.

Gen. Boris Gromov, the last commander of Soviet troops in Afghanistan, was named as Pugo's principal deputy. Gromov, who probably has more combat experience than any other Soviet general, has been an outspoken critic of liberal trends in Soviet society and is widely regarded as one of a handful of top commanders with political ambitions.

The full significance of today's reshuffle is unlikely to become clear for several days, although it appears to signal Gorbachev's intention to take a tougher line on law and order. In the past, the Soviet leader frequently has balanced dismissals of progressive politicians with moves against conservatives.

The changes appear to be the first step in what is likely to be a major government overhaul in coming weeks. Gorbachev, who was severely criticized by many deputies last month for presiding over what has been viewed as a paralysis of political power, is due to present detailed proposals to the legislature this week on a package of measures to streamline executive authority under his control.

An energetic reformer in the Gorbachev mold, Bakatin had earned the trust of Soviet intellectuals and radical politicians, even though he did not ally himself directly with any political group. But he was a favorite political target for an influential conservative lobby in the Soviet legislature, known as Soyuz, which blamed him for ethnic disturbances that have cost several hundred lives this year.

In addition to being responsible for a 700,000-strong police force, the Soviet interior minister also controls about 400,000 Interior Ministry troops and special anti-riot squads. These troops have been deployed in many parts of the country to curb nationalist disturbances and would almost certainly bear the brunt of enforcing any future crackdown.

Today's appointments suggest that Gorbachev is eager to ensure smoother cooperation among the army, the KGB and the Interior Ministry -- the three institutions that effectively control the still-powerful repressive apparatus of the Soviet state. Pugo, a protege of former Soviet leader and KGB chief Yuri Andropov, will be well-placed to coordinate action with the KGB, while Gromov has the confidence of the military command.

Over the past few weeks, Soviet politicians and commentators have openly speculated about the possibility of a "hard-line solution" to the Soviet Union's deepening ethnic and economic crisis. Gorbachev has responded by reiterating his commitment to democratic change while at the same time taking measures designed to reassure the armed forces and Communist Party conservatives.

In another move to reassure the military, Gorbachev on Saturday vetoed any attempt by the Soviet Union's 15 republics to defy Soviet draft laws or set up their own military detachments. Soviet military leaders, including Defense Minister Dmitri Yazov, have appeared on television in recent days saying they will not allow the army to be "mocked."

The announcement of the new Interior Ministry lineup sent a chill through the ranks of radicals. The Russian republic's justice minister, Nikolai Fyodorov, a close ally of populist politician and Russian President Boris Yeltsin, described Bakatin as "a figure of hope" whose replacement appeared to presage a "harsher" approach to law and order.

Tass said Pugo's appointment would have to be ratified by the Supreme Soviet, the federal legislature, but there seemed little risk it could be overturned. After heading the Latvian branch of the KGB, Pugo served as Communist Party leader in Latvia from 1984 to 1988. He is one of the few prominent Balts not to throw their weight behind new nationalist movements seeking full independence from the Soviet Union.

In addition to Gorbachev's plans for further government changes, the Soviet leader also has promised a shake-up in the Soviet military command, leading to speculation that Yazov may soon be replaced.

The Associated Press added from Moscow:

Forty tons of donated food and medical supplies arrived today in the first of what is expected to be a series of shipments by the Connecticut-based aid organization AmeriCares aimed at easing Soviet shortages.

Soviet television showed soldiers and students unloading medical supplies from a cargo plane. Shortages worsened dramatically this winter.