In the harshest crackdown on political dissidents in four years, 11 persons have been sentenced to prison and 14 others arrested for involvement in a political organization that Kenyan President Daniel arap Moi says advocates "evil against the state."

The continuing arrests -- and the sentencing of several defendants to prison without access to legal counsel -- mark the most aggressive government action against its critics since an attempted coup was put down in 1982.

Those imprisoned allegedly are members of an underground political organization called Mwakenya (a Swahili acronym for Union of Nationalists to Liberate Kenya) and have been convicted of possessing or distributing "seditious" publications.

Moi, whose policies are never publicly criticized by local politicians or the local press, has blamed Mwakenya on certain "bearded people," a reference to intellectuals. Many dissidents held in jail have connections with the country's universities, either as teachers or students.

"No ordinary Kenyan is a member of Mwakenya, and you should be careful with these bearded people because they are merely serving their foreign masters," Moi said. "When you see bearded people, you should know they lack something."

One Mwakenya leaflet, delivered this month to western embassies, condemns Moi for "dictatorial rule." The leaflet, among other things, accuses the president of economic mismanagement, corruption and "forced family planning and tubal ligation to unsuspecting mothers."

Western diplomats and mid-level Kenyan officials agree that the circulation of dissident literature presents no significant threat to the stability of the government. These sources say they have seen no evidence of outside governments trying to destabilize Kenya.

Since an Air Force-led coup was crushed in 1982, Moi's power and popularity have grown steadily. Kenya has become a one-party state with Moi as the unquestioned boss of both the party and the government.

In addition, Kenya is in its strongest economic position in years, the result of high world prices for coffee, the country's major export, along with a record corn crop and low oil costs. Economists say Kenya's government is among the best-managed, least-corrupt in Africa.

It remains unclear to political observers here why Moi has taken the Mwakenya threat so seriously. There is no doubt, however, that the president's concern has filtered down through his government.

Kenya's chief magistrate, H.H. Buch, while sentencing one law student to four years in prison, warned that Mwakenya coup-plotters "would have plunged the whole country into total chaos" without government action.

Defending the arrests and prison sentences, Moi asked in a speech on April 12: "Has anybody been jailed for doing nothing? Kenya is a free country and only those who commit evil against the state are jailed."

The Kenyan government, responding to international publicity about its crackdown, recently has been intercepting critical foreign publications mailed into the country.

It confiscated many of the April 9 copies of "Africa Confidential," a bimonthly journal of African affairs that is mailed in an unmarked envelope. The issue carried a lead article about recent arrests, problems in Moi's government and the president's personal wealth.

Besides those arrested or already sentenced to prison, two lecturers from the University of Nairobi have been "detained" by the government in the past two months under the Public Security Act, a law that allows the government to deprive suspects of constitutional safeguards indefinitely without specifying why they are being held.

The reference in the Mwakenya leaflet to the government's purported "forced family planning" is significant in that the sedition arrests here began in late February following widespread rumors that the government was giving school children milk laced with birth-control drugs.

The false rumors, which sent some school children jumping out school-house windows when milk was delivered, infuriated Moi, who personally introduced the school milk program in primary schools. The president also has been an outspoken advocate of family planning to help reduce Kenya's high population growth rate.