Yugoslavia's communist authorities today imposed emergency measures in an attempt to quell mounting disturbances among the country's politically sensitives ethnic Albanian minority.

Serious clashes between demonstrators and security forces in the province of Kosovo, which borders on Albania, have triggered the first crisis in Yugoslavia since president Tito's death 11 months ago. The gathering unrest reached a climax yesterday when, according to official sources, several hundred people were injured as police firing tear gas broke up a march of at least 10,000 protesters through the provincial capital of Pristina.

Under the emergency measures, all public gatherings and movement by "group of people" are banned in the province -- Yugoslavia's poorest region. Army units have been called into protect public buildings, including Pristina's town prison that was the target of yeaterday's march.

The protesaters, who included university students and miners, were demanding the release of people detained following riots over the last month. Officials said that demonstrators, some of them armed with guns and firing at the police, pushed children in front of them to make it more difficult for the security services to disrupt the march.

Kosovo has long been regarded as one of the weak points in post-Tito Yugoslavia because of its economic backwardness and rivalry between the province's ethnic Albanian majority and Serb minority. Years of what Kosovo's million Albanians considered repression by the Serb elite last boiled over in 1968 when violent demonstrations had to be quelled by the Army.

In a nationwide television broadcast, Kosovo's president, Dzavid Nimani, accused the demonstrators of being manipulated by "enemy forces" wanting to destroy Yugoslavia -- a federal state made up of many different national groups. Some of the marchers are said to have chanted slogans calling for unity with Albania, a militantly communist neighbor state, but the main demand was for Kosovo to be upgraded from a province into a republic.

A complicating factor is the reported serious illness of Albania's isolationist leader, Enver Hoxha, 72, who succeeded in breaking away from Soviet domination in 1961. One of the "nightmare scenarios" for post-Tito Yugoslavia is of the Kremlin somehow regaining control over Albania after Hoxha's death and fomenting unrest among the Albanian minority here.

The latest round of disturbances began March 11, when about 2,000 students at Pristina University rioted over poor living conditions and inequality. The riots were suppressed by police and the discontent has now spread both to other sections of the population and other parts of the province.

Serious incidents have been reported in half a dozen towns in Kosovo over the past three weeks, including Pec, where the refectory of a Serbian monastery was burned in mysterious circumstances. This created the danger of a backlash among Serbs, Yugoslavia's largest national group, for whom the patriarchate of Pec has great historical and emotional significance.

Taken together, the latest events reflect the two gravest problems confronting Tito's successors: ethnic differences in the complex multinational state and an increasingly serious economic crisis. Inflation is running at more than 40 percent, there are 800,000 unemployed in a total population of 22 million, and Yugoslavia is heavily in debt.

The economic problems are most pronounced in poor provinces such as Kosovo, despite a program of large scale investments over the last 10 years. One fear of Yugoslav leaders is that economic strains in less developed parts of the country could trigger new political tension.

The comparison with Poland springs to mind, but Yugoslavia is very different. Its multinational make up virtually precludes a protest from a largely united population, as in Poland. Tito, during his 35-year rule, excelled in playing one nationality against another.

In addition, there are more outlets for tension than in Poland. Yugoslavs are free to travel abroad and, to a limited extent, participate in political and economic decision-making through the system of workers' self-management.

Nevertheless, the latest disturbances do represent the most serious ethnic unrest to have erupted in Yugoslavai for a decade. In his televised speech, President Nimani said the authorities were determined to use all necessary measures to safeguard public order.

A statement from the provincial Interior Ministry said the emergency restrictions would remain in force "as long as the extraordinary situation in the province continues." Territorial reserve units, normally intended to serve against an external enemy, have been mobilized to assist the police and security services.

Officials said meetings were bing held in factories throughout Kosovo to drum up support for the firm stand taken by the authorities. Local Communist Party branches have sent telegrams to Yugoslavia's collective leadership condemning the disturbances and pledging their loyalty.

Last week official said 21 students were detained following a 24-hour occupation of Pristina University.

The flare-up coincided with the arrival in the province of a ceremonial baton that youths carried around the country to mark Tito's birthday. The annual event is intended to demonstrate unity and brotherhood among the south Slay nations.