UPDATE 2-Venezuela to sell debt to up parallel bolivar-source

* Injects 3 month, zero coupon paper to strengthen bolivar

* Plans regular intervention, aims for rate of 5 to dollar

* Bolivar strengthens after news (Adds byline, comment, details)

By Ana Isabel Martinez

CARACAS, Jan 13 (Reuters) - Venezuela's central bank will on Wednesday sell $50 million in short-term bonds to strengthen the unofficial black-market bolivar rate after the country devalued its currency last week for the first time in five years.

Venezuela's President Hugo Chavez last Friday set two official rates for the bolivar and repeatedly said he aimed to bolster the value of the currency on freely floated parallel market, or black market.

"In few minutes we should announce an auction of very liquid dollar paper," the source told Reuters. "This is a permanent policy that will take place according to the behavior of the market."

The source said the bank will regularly inject 3-month, zero coupon dollar bonds with the aim of keeping the bolivar at about 5 to the dollar on the parallel.

Chavez is a strong believer in state intervention in the economy and has nationalized many industries in the OPEC nation. He uses currency controls to prevent capital flight.

By strengthening the bolivar on the black market, he hopes to minimize inflation triggered by devaluation, which would increase the cost of imports in bolivars.

On Wednesday, the bolivar strengthened to around 5.7 against the dollar from as low as 6.5 the day before on the parallel market VENFM=RR LCDEBT. Precise exchange rate data is not circulated publicy in the local foreign exchange market, which operates with mechanisms including bond swaps.

With thousands of Venezuelans piling into shops to buy goods before prices rise, Chavez has sent soliders to monitor shopping districts and close retailers accused of gouging.

The bolivar had been fixed at 2.15 to the dollar for five years before the devaluation, which set a new rate of 2.6 applicable to basic goods and another of 4.3 "petro-dollar" rate for non-essential purchases and oil income.

The thriving parallel market was used to buy dollars for about 50 percent of imports last year, economists say. The parallel rate is often weaker than 6 bolivars to the dollar.

The interventions in the bolivar market will take place via banks and the bourse, the source said.

The government has never before openly intervened in the parallel market.

The price of Venezuela's highly traded global 2027 bond VENGLB27=RR dropped 1.7 percent to bid 81.500 on Wednesday, retreating after a major rally at the start of the week on news of the devaluation.

(Reporting by Ana Isabel Martinez; Editing by W Simon)