Chicago (AFP) - Greg Pence, the older brother of US Vice President Mike Pence, won a seat in the US House of Representatives on Tuesday soon after polls began closing in the midterm elections.

The 61-year-old businessman and military veteran claimed victory for the Republicans in the district his younger brother once held in Indiana.

Prior to becoming Donald Trump's vice president, Mike Pence went from serving in heavily-Republican 6th district in southern Indiana to become governor of the conservative Midwestern state.

In his first campaign for public office, the elder Pence promised to support the agenda pushed by his brother and Trump in Washington, describing himself as a conservative who opposes abortion and supports gun ownership rights.

With less than a fifth of votes counted, Pence declared victory with 68 percent and was projected as the winner by US networks CNN and NBC.

"Like many of you, I continue to be inspired by President Trump," Pence said in his victory speech.

"I support the president's agenda to fight for the middle class and ensure commonsense policies get through and accomplished by Congress."

Pence's opponent was Democrat Jeannine Lake, a self-described Christian Democrat who supported tuition-free college and universal healthcare, and opposed Trump's trade tariffs that she said had financially hurt farmers.

Pence will fill an open seat vacated by Luke Messer, who ran unsuccessfully for the Senate.