The Foreign Ministry invoked the March 2013 memorandum of understanding between the two countries that all court procedures referring to old LB deposits in Croatia that were paid out by the Croatian state after the break-up of Yugoslavia be suspended until a solution is found as part of Yugoslavia succession talks.

"Today's decision...constitutes yet another violation of the memorandum," the ministry said.

In a ruling that is not yet final, the Zagreb Municipal Court ordered the defunct Slovenian bank Ljubljanska banka (LB) and Nova Ljubljanska banka (NLB) to pay US$9.1m plus to the Croatian PBZ bank plus EUR 420,000 in legal costs.

The judgement was based on the Zagreb court of second instance ruling that the conditions for suspending or staying the procedure did not exist.

The judgement confirmed PBZ's standing as claimant on the basis of an agreement with the Croatian government that empowers PBZ and the Zagrebačka banka bank to sue for LB deposits that had been guaranteed and paid out by Croatia through the two banks.

The ruling upholds the previous assessments by Croatian courts that the Mokrice memorandum does not constitute an international treaty, while rejecting the defendants' claims the Croatian court did not have the jurisdiction in the case.

The Slovenian banks are expected to appeal against the ruling.

The Croatian banks brought a total of 27 lawsuits against LB and NLB between 1994 and 1996 over LB deposits that were transferred to Croatian banks and paid out by Croatia.

According to Slovenian sources, 76,000 Croatian citizens transferred savings deposits totalling 545 million Deutsche marks (EUR 272.5m) from LB to 25 Croatian banks. The bulk of the money was paid out by PBZ (EUR 64.5m) and Zagrebačka banka (EUR 94m).

Over more than two decades the 27 cases have been merged into 15 cases before Croatian courts. Rulings in two of the cases have become final, one in favour of the Slovenian banks and one in favour of the plaintiffs. In each of the cases the sums were below EUR 800.

Slovenia has appealed to the Croatian Constitutional Court, whose decision is still pending.

In four repeated procedures before today's ruling, Croatian courts decided in favour of the plaintiffs and the defendants appealed. In nine of the cases decisions are still pending.

The issue is separate from the LB deposit holders who did not opt to transfer their savings to Croatia, and who will be compensated by Slovenia under a 2014 ruling by the European Court of Human Rights.

Under this ruling Slovenia will have to compensate around 230,000 account holders of former LB subsidiaries in Sarajevo and Zagreb.