In its latest assessment of the three banks, the agency first downgraded the viability ratings of all banks to f- from ccc (NLB and NKBM) and cc (Abanka Vipa) before upgrading them to b-.

The downgrade "reflects Fitch's view that the banks failed, based on the full write down of their equity and subordinated instruments, and the scale of their recapitalisation requirements," Fitch said in a press release.

"The subsequent upgrades of the viability ratings to b- reflects the agency's view, based on preliminary analysis of the banks' post-rescue capital, asset quality and coverage ratios, that the banks should be able to achieve viability ratings of at least in the b category."

The banks were also placed on Fitch's Rating Watch Positive list, which means that their viability ratings could be upgraded again.

The agency moreover pointed out that the government believes NLB and NKBM will report core Tier 1 ratios of 15% at end-2013 following the transferral of non-performing loans of the Bank Asset Management Company (BAMC).

Moreover, Abanka is expected to report a Tier 1 ratio of 9% by end-2013, subsequently rising to 15% in the first quarter of 2014, the agency says.

The changes in ratings come "after the approval by the European Commission of state aid measures in respect of NLB and NKBM, and of rescue aid measures in respect of Abanka. As a result, the Slovenian government has recapitalised, and in so doing fully nationalised, the three banks."