Europe's new top graft fighting body will probe the "powerful", "rich" and "dangerous", its head warned Friday on her first visit to an EU member since taking up her post.

The Luxembourg-based European Public Prosecutor's Office (EPPO), headed by Laura Codruta Kovesi, a former Romanian anti-corruption chief, started work this month.

The independent outfit has the job of cracking down on fraudulent use of EU funds and fight cross-border VAT fraud, money laundering, and corruption.

"We will investigate all those who commit crimes that fall under our jurisdiction. Because we have to prove that the law is equal for everybody," Kovesi told reporters in the Bulgarian capital Sofia.

"Yes, we will also investigate powerful people, yes, we will investigate rich people, yes, we will investigate dangerous people."

She also warned that if anyone tried to interfere with the EPPO's work, "I will make this public."

The central office has 22 European prosecutors who will oversee cases from member states and approve the main decisions in an investigation, such as indictments.

EPPO also has a network of 140 European delegated prosecutors sitting in member states' capitals, but working for the Luxembourg office under their own criminal code.

Kovesi said she had travelled to Bulgaria to settle the appointment of ten deputy prosecutors to the EPPO.

The body only validated four of Bulgaria's candidates, saying the six others failed to meet the required criteria.

"It is one of the member states where we don't have the entire team," she said. "If we cannot work with proper resources it is a problem for the EPPO, and we cannot be efficient."

She added from her discussions on her two-day visit the procedure to propose six new candidates would start next week.

Bulgaria saw massive anti-corruption protests last summer. According to Transparency International, it is the most corrupt among the EU's 27 members.

The US last week blacklisted six Bulgarians -- including a notorious media mogul, as well as an ex-gambling tycoon -- for their "extensive" roles in corruption, sparking a fresh round of demonstrations.