The Office of the Attorney General of Switzerland (OAG) has blocked various bank accounts in Switzerland over an alleged oil bribery scheme linked to Nigeria.
This came as executives from oil giants Shell and Eni are due to stand trial in Milan, Italy, in May.
In a statement from its website, it stated that at the request of the Milan public prosecutor, the Swiss authorities confiscated assets and provided information and assistance to the Italian authorities, the Swiss attorney generalâ€™s office confirmed this on Monday.
The trial, which was supposed to hold on Monday, was postponed until May 14, Reuters reported.
Nigerian and Italian courts have accused officials from both companies of having paid bribes to secure a licence for an oil field off the African country.
The case has been billed as one of the biggest ever corruption cases in Europe by anti-corruption campaigners.
The exploration permit, which concerns an oil block called OPL-245 in the Gulf of Guinea off Nigeria, was issued in 2011 by the Nigerian government to the two firms for $1.3 billion.
Three separate bank accounts in Lugano, Basel and Geneva were blocked, according to a report in German-speaking Tages-Anzeiger newspaper on Monday.
The prosecution confirmed this, but declined to comment on the value of the assets which were seized. The Tages-Anzeiger cited â€œseveral hundred million francs,â€ while the Nigerian authorities quoted a bribery sum of $801 million.
In all, 13 people have been accused, including Eni boss, Claudio Descalzi, and his predecessor Paolo Scaroni, two former top Shell managers, former Nigerian oil minister, Dan Etete and a series of middlemen and advisers.
The companies themselves are also corporate defendants. Both oil companies have denied wrongdoing and expressed confidence that the trial would exonerate them and the individuals.