SALISBURY, Rhodesia--Nationalist guerillas blew up oil storage tanks and attacked at least five polling places yesterday as Rhodesians prepared to vote today for the nation's first black-majority government.

The raids threatened the government's effort to encourage a solid turnout of black voters that would help legitimize the elections in the eyes of the international community.

Army Brig. Gen. Peter Rich said yesterday attacks on polling places began Sunday night, but only one site suffered damage. Rich said two guerillas were killed in the attacks.

The Patriotic Front forces of guerilla leaders Robert Mugabe and Joshua Nkomo have pledged to sabotage the voting for the 72 black members of Rhodesia's first majority parliament.

The guerillas oppose the elections because whites would retain control of the police, security forces, judiciary and civilian administration, 28 seats in the 100-member parliament and four cabinet posts. White Rhodesians voted last week for their parliamentary representatives.

The military reported that one million gallons of diesel fuel and thousands of gallons of gasoline were destroyed in a rocket attack Sunday night at a storage depot in Fort Victoria.

Military sources said six guerillas used a Russian-manufactured rocket in the attack. The petroleum is valuable to Rhodesia because its imports are restricted by United Nations sanctions.