(CNN) -- Two Democratic state senators in Wisconsin defeated Republican challengers to hold on to their seats in a recall election Tuesday, news media in the state reported.

Tuesday's win by the Democrats was the last round in a series of recall elections this summer.

Both Democratic incumbents, Sen. Jim Holperin and Sen. Bob Wirch, survived.

The Wisconsin Government Accountability Board, which certifies election results, said official results will not be released until next week. The unofficial results released Tuesday were collected by The Associated Press and distributed to newspapers, television and radio stations.

Last week, six Republicans were the subject of a recall. Four of the six won. Last month, a Democratic senator also won a recall election.

GOP retains Wisconsin Senate control

The recall elections stem from the bitter battle last winter that saw pro-union protesters camping out in the state Capitol and Democratic senators fleeing the state in an unsuccessful attempt to halt legislation by Wisconsin Gov. Scott Walker that some felt was anti-union.

Democrats were angling to win GOP-held seats to capture control of the upper chamber. Before the elections, Republicans held a 19-14 majority in Wisconsin's state Senate.

With Tuesday's results, the Republican retained their majority but narrowly: 17-16.

"Tonight's election wins continues to show that the people of Wisconsin are looking for a check on Scott Walker's reckless and radical agenda," Phil Neuenfeldt, president of the Wisconsin branch of the AFL-CIO, said.

Walker set off a firestorm in January when he moved to curtail the collective bargaining rights of most state employees.

With majorities in both houses of the Legislature, Walker and his GOP allies voted to limit raises for public employees except police and firefighters to the rate of inflation, bar unions from deducting dues from workers' paychecks and force them to hold a new certification vote every year.

Republicans insisted that the legislation was necessary to control skyrocketing public employee benefit costs and close a budget shortfall, while Democrats called it an attempt to gut public-sector labor unions, one of their core constituencies.

The state Supreme Court upheld the legislation in June.

CNN's Jessica Jordan contributed to this report.