Albanian prosecutors say they have questioned opposition Democratic Party leaders about suspicious spending abroad of $650,000 during parliamentary elections two years ago.

A statement by the Tirana prosecutor's office on Monday said Democrats' leader Lulzim Basha and three other politicians were questioned on why their party had not declared the money spent in United States and Scotland.

Basha denied breaking any laws, saying that responses from the authorities in the United States and Britain "prove that the Democratic Party and its leaders have not broken any law."

The U.S. publication Mother Jones has alleged that the Democrats received secret funds from Russian sources using a U.S. lobbyist, Nick Muzin, who was paid by a Russian-linked company called Biniatta Trade.

The center-right Democrats have rejected the allegations.