Federal prosecutors indicted a US congressman and his wife Friday on bribery and money laundering charges connected to a bank in Mexico and an energy company owned by Azerbaijan.

Henry Cuellar, a Democrat from Texas, accepted around $600,000 in exchange for advancing the interests of the bank and the former Soviet Republic over seven years through at least November 2021, according to the indictment.

"In exchange for the bribes paid by the Azerbaijani oil and gas company, Congressman Cuellar allegedly agreed to use his office to influence US foreign policy in favour of Azerbaijan", the Department of Justice (DOJ) said in a statement.

"In exchange for the bribes paid by the Mexican bank, Congressman Cuellar allegedly agreed to influence legislative activity and to advise and pressure high-ranking US executive branch officials regarding measures beneficial to the bank."

The DOJ alleges that the bribes were laundered into shell companies owned by the 68-year-old congressman's wife Imelda Cuellar, who was indicted alongside him.

The couple surrendered to the authorities on Friday and were released on bail.

They are facing more than a dozen counts each -- ranging from bribery and conspiracy to commit wire fraud to money laundering -- and could be looking at prison sentences lasting decades if convicted.

Cuellar, who represents a stretch of Texas stretching from San Antonio to the Mexico border, released a statement denying any wrongdoing by the couple, and said it would not stop him running for reelection.

"The actions I took in Congress were consistent with the actions of many of my colleagues and in the interest of the American people," he said.

FBI agents raided Cuellar's home and campaign office in 2022 as part of a probe into ties between oil-rich Azerbaijan and a group of US businessmen.

The centrist -- one of the few anti-abortion Democrats in Congress -- saw off a challenge from a progressive rival to be reelected even after the scandal broke.

Hakeem Jeffries, who leads the Democratic minority in the House of Representatives, said Cuellar is "entitled to his day in court and the presumption of innocence" but would step down from a top subcommittee posting.