Three impoverished Andean provinces were placed under a 30-day state of emergency last night by the government of President Fernando Belaunde Terry as a result of surging leftist guerrilla activity in the south and central highlands in recent weeks.

The decree is the fourth suspension of individual guarantees to be imposed on provinces within the region in less than a year and affects more than a quarter of a million people living in the provinces of La Mar, Cangallo and Andahuaylas.

The government also announced it had sent 100 police trained in antisubversive warfare into the rugged area, 360 miles southeast of Lima and midway between the capital and the ancient Inca city of Cuzco.

In the last two weeks five policemen, two civilians and two guerrillas have died in attacks on police stations and large farms. The guerrillas are believed to be members of Shining Path, a Maoist organization that police say has some 400 militants, mostly in the south-central region. It is an area of spectacular mountains, remote valleys and some of the grimmest poverty in Peru.

In a pamphlet being distributed here, Shining Path has declared the beginning of guerrilla warfare and claimed responsibility for some 2,900 acts of violence. The circular, entitled "Let's Get the Guerrilla War Moving," is the first attempt by Shining Path to explain its goals

According to police officials here, some 40 people have died in terrorist attacks in the two years since Belaunde assumed power following the first democratic election in more than a decade.