UEFA is investigating complaints from Luxembourg and Portugal that Ukraine fielded an ineligible player in Brazil-born Junior Moraes for their recent Euro 2020 qualifiers against the two countries, European football's governing body announced on Wednesday.

"Following a protest lodged by the Luxembourg Football Federation and the Portuguese Football Federation, disciplinary proceedings have been instigated... in relation to the eligibility of Ukraine's player Junior Moraes in the above-mentioned matches," UEFA said in a statement.

Attacker Moraes made his Ukraine debut as a substitute in Friday's goalless Group B draw with Portugal after receiving citizenship from the country a few days previously.

He made his first start for Andriy Shevchenko's side in Monday's 2-1 win over Luxembourg.

The 31-year-old has played most of the past seven years in Ukraine, this year for Shakhtar Donetsk.

FIFA rules state that for players to acquire a nationality they have to live continuously in the country for five years, and Portuguese media claims he does not meet this criteria due to his spell in China in 2017.

Group B leaders Ukraine risk losing all four points earned and forfeiting both games if Moraes is judged ineligible.