The seizure of assets as part of a probe into suspected fraud against Italy's Monte Paschi has frozen the so-called "Alexandria" derivatives contract with Japan's Nomura <8604.T>, a source close to the investigation said on Tuesday.
"The seizure order interrupts the validity of the contracts so they cease to have effect," the source said. "The contracts have been frozen, so receipts and payments are suspended."
The "Alexandria" contract is one of the central elements in a complex investigation into the scandal at Monte Paschi, Italy's third-largest bank, which got into trouble over a series of opaque derivatives deals linked to the 2007 acquisition of rival Banca Antonveneta.
No comment was immediately available from the banks.
Earlier, Siena prosecutors said they had seized assets worth more than 1.8 billion euros held by Nomura as well as by a group of former Monte Paschi managers including ex-chairman Giuseppe Mussari.
(Reporting by Stefano Bernabei; writing by James Mackenzie)