While East Germany continues to pressure dissident writers and artists to leave, it also appears to be stepping up arrests of persons allegedly working as spies for West Germany.

In the last five months, 13 such arrests have been reported in the East German Communist Party newspaper, Neues Deutschland - four of them in the past 10 days.

The arrest reports normally appear in the same place in the newspaper, as one-paragraph stories in the lower left-hand corner of Page 2. Usually no names are mentioned, and it is not stated whether the person arrested is East or West German - only that he or she is in the service of West German intelligence agencies.

Western officials say they have not taken note of the number of such cases being reported lately and have no idea who the people are or what is happening to them. They offer varying theories for the phenomenon.

Some suggest that the East Germans may not have stepped up the frequency of arrests, but rather the number they decide to publicize.

In this view, East Berlin may be seeking to pump up the reputation of the state security service while tactly warning the population that contact with visiting West Germany may be dangerous.

The notices may also be part of a spreading pattern in many Soviet-Bloc countries, perhaps linked to the East's attempt to build up ammunition in case it is attacked over human rights at the Belgrade conference to review the 1975 Helsinki agreement.

On the other hand, those reportedly arrested may be spies. Both East and West Germany have hordes of agents operating in each other's territory, and lately the West German security agency seems to have been getting the better of its Eastern counterpart in uncovering spy operations.

Recently the East Germans also arrested one of their own dissidents, economist and Communist Party member Rudolf Bahro, on suspicion of espionage.

The Bahro case is viewed as especially significant, since it is the first time an East German dissident has been arrested for possible "secret service activity."

Bahro got into trouble after talking about his banned book in an interview on West German television. The book charge that the East Berlin government is "caught in a spiderweb of bureaucracy, bogged down in Stalinist theory and led by a Politburo that talks to itself."

Although the East Germans have occasionally resorted to harsh measures for some dissident artists and writers, especially those who are not prominent, they have generally chosen to try to force such critics to emigrate, avoiding potentially damaging strong-arm tactics or show trials against well-known figures.

But lodgings suspicions of spying against Bahro, as some specialists here see it, provides East Berlin with the means to use stronger police tactics and perhaps suffer less private criticism among segments of the East German population.

Bahro's book, "The Alternative," calls for a radical change toward liberalization. The manuscript was slipped out to the West last spring and the book is to go on sale here soon.

Apparently anticipating his own arrest, Bahro also slipped at taped interview with himself out to the West, and reporters heard the economist demand the East Germany abolish its "Stalinist constitution" because "It cuts deep into life, because it is unproductive, because it ties up and cripples personal drive, which it then misuses by entering a competition withthe West which can never be won this way."