GLENDALE, Calif.--Police said yesterday they arrested the 17-year-old son of a Philippine newspaper executive and the youth's girlfriend for investigation of murder, alleging the two killed Oscar Salvatierra and used political turmoil as a cover for the deed.

Police Chief David J. Thompson said that the since the killing Wednesday, "there has been widespread speculation that Salvatierra's death was politically motivated" by supporters of Philippine President Ferdinand E. Marcos.

But, the chief said, "Our ongoing, thorough and exhaustive investigation has discovered no evidence whatever to support that position." On the contrary, he said police believe Salvatierra's death was the result of domestic violence within the home and committed by his son, whose name was not released because he is a minor.

Salvatierra, 41, who received a mailed death threat the day before he was shot to death at his home, worked in the Los Angeles bureau of the Philippine News, a San Francisco-based weekly that has been critical of Marcos. Salvatierra worked to increase circulation and advertising, and was not a writer.

The two were taken into custody based on "reliable and corroborated statements provided to this department by an informant," Thompson said. The girlfriend was identified as Teressa Kay Deburger, 18, a Glendale High School student.

Meanwhile, in Manila, Marcos said yesterday that sore losers and "modern-day imperialists" in foreign capitals are trying to taint his election victory. The critics he castigated say he won by fraud.

Leftist groups pledged support for boycotts, strikes and demonstrations planned for next week by Corazon Aquino, who claims she won the February 7 election. Marcos was declared the winner by the National Assembly, in which he controls two-thirds of the seats.

A national police captain resigned in support of Aquino, calling the Marcos government "illegitimate, repressive, unjust and corrupt."

The U.S. Senate and European Parliament have passed resolutions accusing Marcos of election fraud, and criticism has come from the Reagan administration and other governments.

Only the Soviet Union sent a message congratulating Marcos on the election victory.

Philip Habib, Reagan's special envoy, met with Aquino for the second time yesterday. Her spokesman said she told him, when asked where her protests might lead, "Wait and see."