Angolan President Joao Lourenco on Thursday compared the fight against corruption in his country to "touching a wasps nest", a day after his predecessor Jose Eduardo dos Santos refuted allegations he emptied the state's finances.Dos Santos, who stepped down in September 2017 following 38 years in control of the oil-producing nation, has been accused by Lourenco of leaving "state coffers empty".Dos Santos hit back against the allegation on Wednesday, insisting: "In September 2017... there was about $15 billion in the National Bank of Angola."At the start of a three-day state visit to Portugal, Lourenco on Thursday reaffirmed his determination to take on graft."When we decided to fight corruption in Angola, we knew that we were touching a wasp nest. We started to feel the bites but that will not kill us and we will not back down," Lourenco told a press conference in Lisbon.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and FacebookAsked how Angola would recover the nation's funds, Lourenco said: "We are not afraid to play with fire. We will continue to do so, being careful to keep it under control."The Angolan government has said it intends to voluntarily or forcibly return illegitimate funds to the country.Despite its oil wealth, Angola remains among the poorest countries in the world.Lourenco has pledged to kickstart the ailing economy with a push to attract foreign investment to end its "excessive" dependence on oil revenue.Since coming to power, Lourenco has fought against corruption while also removing figures associated with the previous regime, including deposing Dos Santos' daughter from the helm of state oil giant Sonangol.Billionaire Isabel dos Santos is Africa's richest woman.