Belgian foreign minister Didier Reynders (Francophone liberal) announced the news on his arrival at a ministerial conference at the UN in New York.
"We congratulated the new president. We definitely have our doubts about the election process, but the most important thing now is to change policy."
Mr Reynders notes the new president's promise to free all political prisoners.
"In the coming weeks and months we will see whether the way the country is led benefits the people more. Congo is rich in raw materials, but many people live in poverty."
Mr Reynders also stressed the need for Congo to restore good relations with the EU. Just before the elections Bart Ouvry, the Belgian diplomat who serves as the EU ambassador, was expelled.