A candidate for Poland's ruling Law and Justice party has won a Senate seat in a by-election, considered an important show of support for the party that has been criticized abroad for its sweeping constitutional changes.

Election officials announced Monday that Anna Maria Anders, the daughter of a Polish World War II commander, won the seat in voting a day earlier in a region in northeastern Poland.

Jaroslaw Kaczynski, the leader of Law and Justice, had said he considered the outcome of the vote a test of support for the party.

Anders is the daughter of Wladyslaw Anders, a general who commanded a Polish army informally called the Anders Army which was formed in the Soviet Union and which fought the Nazis.