Image copyright AP Image caption Kamala Harris (centre) is polling about 40% of the vote in Tuesday's election, according to partial results

Two Democratic women candidates, both from ethnic minorities, will compete in a run-off for California's open seat in the US Senate, officials say.

The face-off between Kamala Harris and Loretta Sanchez marks the first time in the state's history that Republicans will be absent from the Senate race.

The two women came first and second among 34 candidates for the seat that will be vacated by Sen Barbara Boxer.

Only the two top candidates advance to a run-off, California's rules state.

Ms Harris, 51, California's attorney general, is polling about 40% of the vote in Tuesday's election, according to partial results.

Congresswoman Sanchez, who is 56, is trailing far behind with about 17%.

Image copyright AP Image caption Loretta Sanchez (at the microphone) could become one of the first Latinos in the US Senate

If elected in November's run-off, Ms Harris - the daughter of immigrants from India and Jamaica - would become the first woman of Indian heritage to hold a Senate seat and the second black woman in the chamber.

Meanwhile, Ms Sanchez - whose parents are immigrants from Mexico - could become one of the first Latinos in the Senate.

Earlier on Wednesday, Hillary Clinton thanked her supporters for helping her reach a historic moment for women - the US Democratic nomination for president.

Mrs Clinton hailed "the first time in our nation's history that a woman will be a major party's nominee".