* Nearly 16bn euros of debt to be sold at auction
* Debt sales from Italy, Ireland, Portugal and Germany
* Geopolitical tensions continue to dominate
* Euro zone periphery govt bond yields tmsnrt.rs/2ii2Bqr
By John Geddie
LONDON, April 12 (Reuters) - Yields on most euro zone government bonds edged up on Wednesday with nearly 16 billion euros of upcoming debt sales weighing on risk-averse, holiday-thinned markets.
After a number of days in which rising political and diplomatic tensions have put investors off riskier assets, analysts said debt sales from the likes of Italy and Portugal may prove challenging, especially just days before the Easter break.
On the flip side, steep yield falls in safe haven German Bunds suggest there should be demand for Berlin's sale of 10-year debt -- although recent auctions of both two- and five-year bonds have failed.
France is the focus of concern for European investors, with far left veteran Jean-Luc Melenchon surging up the polls to join another anti-EU candidate Marine Le Pen among the contenders for the presidency. The first round vote is on April 23.
Rattling nerves in broader markets, the Syrian conflict has put the United States on a collision course with Moscow, allies of Syrian President Bashar al-Assad, while North Korea warned of a nuclear attack on the United States.
"A veritable glut of government-bond issues will be appearing on what is a rather reluctant market: Italy, Ireland, Portugal and Germany will all be vying for the favour of relatively risk-averse investors," DZ Bank analyst Christoph Kutt said.
"With the market possibly showing a low level of receptiveness, it is quite conceivable that some price concessions will have to be offered at these auctions."
German 10-year yields - the bloc's benchmark - nudged back above 0.20 percent having hit a five-week low of 0.192 percent on Tuesday.
Yields on lower-rated bonds from the likes of Italy, Spain and Portugal were up 2-3 bps on the day.
Italy is set to offer up to 10 billion euros of four bonds on Wednesday, Ireland and Portugal will offer up to 1.25 billion euros in dual bond auctions, and Germany aims to sell 3 billion euros of Bunds. The auctions get underway from around 0900 GMT.
Analysts at Mizuho said there was lukewarm demand for bonds sold by the Netherlands and Austria on Tuesday and that countries selling bonds on Wednesday could see some underperformance.
Investors tend to sell bonds in secondary markets ahead of debt sales to make room in their portfolios for new supply.
"We are expecting a similar dynamic at play today with the large supply slate weighing on outright direction for Bund while countries with bonds on offer today should lag other euro zone government bonds," Mizuho said.
For Reuters Live Markets blog on European and UK stock markets see reuters://realtime/verb=Open/url=http://emea1.apps.cp.extranet.thomsonreuters.biz/cms/?pageId=livemarkets