Dr. Mohammed Naama, head of the Federation of Syrian Dentists, stepped out of his clinic onto a busy Damascus street one afternoon last month and was shot to death by a man on a bicycle who escaped into the crowd.

Like his cousin, President Hafez Assad, Naama was a member of Syria's minority Alawite Islamic sect, whose members dominate the sensitive positions in the country's military and internal security organizations. His death brought to at least 13 the number of Alawites murdered in a little more than a year. Many of them were related to the president by family as well as religious or political ties, according to informed sources here.

The killings have alarmed and provoked the Alawite community, a longscorned and downtrodden minority concentrated in the hills around the port of Latakia, reports here say. The killings appear to be only one element of a sustained campaign by terrorists and dissidents to harass the Assad government.

Explosions and firebombings have hit government buildings, newspapers and army officers' clubs. The foreign minister, Abdel Halim Khaddam, narowly escaped two assassination attempts. The luggage of all hotel guests is searched before they check into their rooms as security officials try to curb the violence, but periodic crackdowns have failed to find the perpetrators of most incidents. When suspects have been punished, new bombings or killings have followed.

The chief of the army's missile corps and the rector or Damascus University, both Alawites have been among the victims.

Diplomatic observers here do not believe that the terror campaign is going to bring down President Assad, who by staying in power for seven years has brought an approximation of stability to a country notoriously difficult to govern. Until Assad seized power, Syria's history since independence in 1946 was a chain of coups and assassinations.

Assad has ended that, but the strains are showing. The inability of the security forces to stop the killings and bombings, added to unrest over corruption, economic setbacks, the military quagmire in Lebanon and the well-known excesses of Assad's brother Rifaat, commander of the "defense and struggle platoons," has caused Assad deep concern.

It showed through in a speech he delivered last month on the occasion of his swearing in for a new seven year term.

He said that "the most important characteristic" of his first term "has been the political stability which has enabled us to strengthen the march of the revolution and to achieve important victories in various fields."

Several times during the speech, he returned to the theme of stability and unity as the basis for national progress, stressing "the importance of political stability and its effect on every aspect of our lives."

Assad urged the people to recognize that "there is no difference between one citizen and another except in the extent of his love for and service to the homeland."

Those ideals have proved difficult to achieve in a nation legendary for intrigue and violence, where most people are orthodox Sunni Moslems who resent the domination of the Alawites.

The Alawites, whose beliefs are described as a blend of the Shai branch of Islam and pagan traditions, constitute only about 11 percent of the population. By joining the armed forces in large numbers while the Sunnis concentrated on business and politics, the Alawites rose to dominance - so much so that Assad himself has promised to broaden the government's base, with little perceptible effect so far.

For many months the government here blamed the rival Arab Baath Socialist Party government in neighboring Iraq for the violence in Syria. It has apparently dropped that line as it became clear that the sources of the trouble was internal.

Informed sources here say the Alawites themselves and government security officials now tend to blame extremists of orthodox Islam, perhaps a revived cell of the shadowy Moselm Brotherhood, for the killings.

For Assad that raises anew the specter that is said to have haunted him throughout his presidency, that factional or sectarian strife would fragment Syria as it did Lebanon.