Two explosions early this morning damaged the entranceway of the downtown offices of Aeroflot, the Soviet airline.

The explosions, which apparently were caused by bombs, came within seconds of each other shortly before 1 a.m. The blasts were heard for blocks around, and federal and local law enforcement officers and demolition experts sped to the scene at the northeast corner of 16th and L streets NW.

There were no reported injuries.

A D.C. fire department official said initial information indicated that "some type of explosive device was thrown at the door" of the offices, which occupy the ground floor of a modern eight-story office building. A D.C. police sergeant at the scene said the blasts might have been caused by pipe bombs.

The explosions broke out a portion of a one-foot wide glass panel that flanks the main doors and extends from floor to ceiling.

In addition, one of the two doors apparently was cracked in the explosion, which attracted a score of passersby and spectators, who stood in a chill mist to watch as investigators arrived, cordoned off the area, and began to search for evidence.

A few minutes after the blasts, The Washington Post was told by a telephone caller with a male voice: "This is the Jewish Defense League. We demand the release of Marina Tiemkin." The caller's next words, only partly audible, claimed that the bombing was in memory of an anniversary connected with Tiemkin. The call ended with the phrase "Never Again," a motto of the league, a militant group.

Six years ago on Feb. 27, several shots were fired at a Soviet diplomatic residence in the Bronx, and United Press International received a telephone call from someone claiming to be "the voice of the Jewish Armed Resistance."

The caller said the shots were fired on behalf of Marina Tiemkin, a Soviet girl then 15 years old. The caller said she had been sent to mental institutions because she wanted to emigrate to Israel.

The Aeroflot offices, about 150 feet from the Soviet Embassy on 16th Street, have been the target of at least two previous bombings.

About 2:30 a.m. on May 10, 1975, a bomb damaged windows at the airline offices. Early on the morning of Sept. 7, 1977, a powerful explosion at the building again shattered windows there.

A caller to UPI said after the 1977 blast that it was in protest of Soviet support of Cuba and the violation of human rights there.

The office was opened in 1974, the year the airline began weekly direct service between Washington and Moscow. Last December, in announcing sanctions against the Soviets in retaliation for alleged involvement in the crackdown in Poland, President Reagan said he was suspending all Aeroflot service here.