Fears were expressed here yesterday that violent purges will soon begin as the new government, headed by Communist Party leader Nur Mohammed Taraki, attempts to consolidate its grip on the country.

Members of the sole party known to oppose the Communists, the Moslem League, have warned of the likely repercussions, and local politicians have suggested that as many as 30,000 members of families loyal to the deposed government may have to be eliminated in order to prevent tribal dissent.

The fears have followed widely accepted but unconfirmed suggestions that perhaps as many as 10,000 people died in last Thursday's coup - a figure which, if correct, would make this one of the most violent political transitions of recent times. The figure of 10,000 dead, while hard to believe, comes from a number of diplomatic and military sources in Afghanistan.

Although the bodies of the slain president, Mohammed Daoud, and his brother, Naeem, who were executed early last Friday morning, are still in a morgue at a military hospital here, the vast majority of the victims of the fighting reportedly have been buried in mass graves on the outskirts of the city.

For all the reported deaths, however, there seem to have been relatively few people injured during the coup, even though the standard battle ratio would suggest that some 30,000 should now be hospitalized if 10,000 were killed. One explanation offered is that most of the casualties were executions rather than battle deaths. People close to the city's various barracks and prisons report volley upon volley of firing within the walls during Friday and Saturday.

Diplomats here expect the Military Revolutionary Council, the supreme ruling body to which Taraki and his 20-member Cabinet are answerable, will shortly begin a wide-spread "cleansing" of the civil service.

"At our hospital all the officials have been sitting around wondering about their futures," said one young doctor. "Those who have any links at all with the Daoud family are terribly frightened about what will happen to them when they are found out."

Following the purge of the civil service - the police and armed forces having been effectively "cleansed" by last week's fighting - the new leaders are expected to turn their attention to the Moslem League, which is strong in rural areas in particular, and to the 30,000 or so members of the Mohammad Zai tribe or "family" from which Daoud and his close friends came.

Experts say a thorough purge may take several months. These same experts say that if the government tries to achieve full control - a situation in which neither the forces of Islam nor those of nationalism or tribal loyalty act against the interests of the Communists now in power - it may well be necessary to "neutralize" as many as 100,000 people. This, they say, could well precipitate a civil war.