Sweden's Defense Ministry took issue sharply yesterday with published reports that attributed secret nuclear test explosions to a research program carried out by Swedish scientists between 1957 and 1972.

A statement issued by Defense Minister Anders Thunborg said Sweden had sponsored a series of "conventional explosion experiments which were undertaken 10 to 15 years ago on the shockwave penetration of various metallic material, including small pieces of plutonium."

But a Swedish Embassy spokesman in Washington said that the explosions had not involved a molecular chain reaction and disputed a headline in yesterday's editions of The Washington Post that said, "Sweden Admits Nuclear Test, Says It Will Not Build Bomb."

The Post story cited an article in Ny Teknik, a reputable Swedish technical journal, which said on Thursday that Sweden secretly had funded a nuclear weapons research program that culminated with l0 small underground plutonium explosions in 1972.

Statements by Swedish officials that were reported Friday by news agencies from Stockholm were concerned primarily with denying that Sweden deliberately had developed the capability to build an atomic bomb, and did not contain the distinction made yesterday by the Swedish Embassy spokesman here and the Defense Ministry between conventional explosions involving plutonium and nuclear explosions involving the same metal.

The embassy spokesman in Washington said the intent had been only to acknowledge that plutonium had been involved in the explosions.

Sweden never has possessed at any one time more than 110 grams of plutonium, while it generally is accepted that 3000 to 5000 grams of plutonium are needed for a nuclear explosion, the spokesman said.

But conventional explosions have been used with small amounts of plutonium to produce molecular chain reactions in experiments by other nations.

In responding to the Ny Teknik article Friday, Prime Minister Olof Palme of Sweden was quoted by The Associated Press as having said that it was sometimes hard to define the limits of "research aimed at protecting the Swedish population against nuclear arms," which is allowed under Swedish law.