* Italian yields at lowest in almost 3 weeks
* Italian govt wins no confidence votes on electoral law
* Portuguese yield hit lowest since Dec 2015
* Euro zone periphery govt bond yields http://tmsnrt.rs/2ii2Bqr
LONDON, Oct 12 (Reuters) - Italy's borrowing costs fell to their lowest level in almost three weeks on Thursday after the government in Rome won two confidence votes on a fiercely contested electoral law that is likely to penalise the anti-establishment 5-Star Movement.
The votes, passed on Wednesday, pushed the premium investors demand for holding Italian debt over top-rated German peers to its lowest since late September.
They also boosted sentiment towards peripheral bonds in a week that has seen tensions between Spain's government and the wealthy region of Catalonia pushing for independence ease.
For now, the focus of bond investors has turned from Spain to Italy, where a third confidence vote is scheduled on Thursday before a final ballot in the lower house on the disputed electoral bill.
The proposed voting system is backed by three of the country's four largest parties, with the centre-left government looking to rush it onto the statute books ahead of an election that is due by May 2018.
Unlike the current rules, the new system would allow the formation of multi-party coalitions before the ballot, a factor likely to hurt 5-Star, which is topping most opinion polls and refuses to join alliances.
"This law does help to a degree in that it reduces the probability of an anti-establishment government, so that could be a slight positive for Italy," said ING senior rates strategist Benjamin Schroeder. "It does also cast a light on election risks coming up."
Italy's 10-year bond yield fell 4 basis points to around 2.13 percent, its lowest level since September 25.
The gap between Italian and German bond yields -- often viewed as a gauge of how investors view relative risks -- narrowed to around 168 basis points, its tightest in almost three weeks.
The strong performance of Italian bonds against euro zone peers came even as markets braced for fresh Italian bond supply later in the day. Investors typically push bond prices down, and yields up, ahead of a bond sale.
Most bond yields in the euro area were slightly lower following the release on Wednesday of marginally dovish minutes from the U.S. Federal Reserve's last meeting.
Fed policymakers had a prolonged debate about the prospects of a pickup in inflation and the path of future interest rate rises if it did not.
Southern European bond markets continued to outpace the rest of the region, with Portugal's 10-year bond yield at its lowest level since December 2015.
Spanish yields fell 3 bps to 1.60 percent, extending falls seen after Catalonia's leader earlier this week stopped short of making a formal declaration of independence.
Spanish Prime Minister Mariano Rajoy on Wednesday gave the Catalan government eight days to drop an independence bid.
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(Reporting by Dhara Ranasinghe; Editing by Gareth Jones)