DACCA, Pakistan, July 26— Handbills prepared by Bengali separatist guerrillas appeared in Dacca today warning the population to begin evacuation of the city in preparation for a terrorist campaign against the Pakistani Army in East Pakistan.

The handbills were distributed in the Maghbazar District of the city a few blocks from the Intercontinental Hotel.

The warning, signed by the Mukti Bahini (Liberation Army), advised residents to move out by 6 P.M. local time.

The public was also warned that vehicular traffic, including taxis and rickshaws, should be off the streets at night from July 28 onward, and that the entire city should be evacuated after Aug. 1.

Bombs have exploded in Dacca every night for the last two weeks, and gunfire often accompanies the explosions. Detonations heard last night could not be immediately explained.

Actions have included the mining of roads in the outskirts of Dacca and bombing attacks against power stations, the city gas supply, homes of persons regarded by the guerrillas as enemies, army installations, bridges and communications.

Army Reacts Swiftly

Reaction by the Pakistani Army is generally rapid and forceful and there have been many arrests of suspects. There also is a steady flow of casualties, according to witnesses, although no estimates of numbers are available.

Army patrols move constantly through Dacca and its environs and military guards are stationed at most important buildings.

Despite this, guerrillas have caused considerable dislocation of essential services since their campaign began two weeks ago and have killed a number of persons.

The Mukti Bahini guerrillas are believed to have been trained in camps in India since March 25, when Pakistani troops attacked in East Pakis tan to quell an autonomy movement.

The Pakistan Army is made up mainly of officers and troops from the Punjab in West Pakistan who speak Urdu. Many Bengalis regard these troops as outsiders and even foreigners.