Portuguese worries hit demand at Greek debt sale, bruise periphery

* Portugal's worries about BES group have regional reverberations

* Greek three-year debt sale sees lacklustre demand

* Irish, Spanish sales go smoothly as markets differentiate (Adds more detail on Portugal, fresh comments, updates prices)

By Marius Zaharia and Emelia Sithole-Matarise

LONDON, July 10 (Reuters) - Concern about the health of a parent company of Portugal's largest bank hurt bonds from the euro zone's periphery on Thursday, curbing demand at Greece's second debt sale following its 2012 default.

It was the first significant episode of contagion for peripheral markets in 2014. Debt yields in those markets reached record lows in the first half of the year, helped by ultra-easy European Central Bank policies that let countries sell debt easily regardless of their ratings or economic situation.

Espirito Santo Financial Group, the largest shareholder in Portugal's Banco Espirito Santo, said on Thursday it had decided to suspend its shares and bonds, citing "material difficulties" at its parent company, ESI.

Separately, Portugal's securities market watchdog, CMVM, said it was analysing a major investment by Portugal Telecom in the debt of Rioforte, a holding company of the Espiroto Santo group.

Sources told Reuters on Wednesday that Espirito Santo was considering debt-for-equity swaps and may ask for more time to repay debts, as it grapples with the financial problems.

The government in Lisbon has repeatedly said that BES is isolated from the holding company's problems and there is no risk to public finances. However, the turmoil has led to a sharp sell-off in Portuguese government bonds and had repercussions for other markets as well.

Greece's sale of three-year bonds drew mediocre demand compared with recent offerings from euro zone peripheral issuers. Athens raised 1.5 billion euros, well below the 2.5 billion to 3 billion euros it was widely expected to achieve.

Total bids were only 3 billion euros. That looked lacklustre to many market players who are used to seeing order books several times that size at a peripheral euro zone debt sale.

Spain's Banco Popular Espanol, meanwhile, was forced to postpone the sale of contingent convertible debt citing poor market conditions, according to a lead manager on the planned deal.

Guido Barthels, chief investment officer at Luxembourg-based Ethenea, was initially interested in the Greek bond sale but was put off by what was happening in Portugal.

"It is not a good day to come to the market for Greece," Barthels said. "Given what's happening in Portugal, it does not make a whole lot of sense to touch that."