* Spot LNG prices contracted in March at $18.30/mmBtu
* Samples likely account for 10 pct of all purchases (Adds details on LNG survey and pricing)
TOKYO, April 25 (Reuters) - Japan on Friday started releasing average prices for spot liquefied natural gas (LNG) to add transparency to an opaque market and amid concern about rising fuel costs in the wake of the shutdown of nuclear plants after the Fukushima crisis.
The move by Japan's trade ministry is most likely the first time that an average spot price has been publicly released based on actual transactions, Takashi Ishizaki, the trade ministry official in charge of the initiative, told Reuters.
Japan takes in about a third of world LNG shipments, importing a record 87.73 million tonnes in the year through March. The average spot price is based on about 10 percent of the super-chilled fuel bought by Japan, according to Ishizaki.
Japan has been importing record volumes of LNG to run power stations following the meltdowns at the Fukushima Daiichi plant north of Tokyo after the March 2011 earthquake and the ensuing shutdown of all 48 reactors in the country.
That has helped to push prices for LNG LNG-AS to above $20 per million British thermal units (mmBtu) across Asia in early March, as North Asian buyers stockpiled fuel after a cold winter amid supply disruptions, notably in Angola.
According to the first LNG survey, prices for spot shipments to Japan contracted in March averaged $18.30 per mmBtu on a delivered ex-ship basis, the trade ministry said on Friday.
At the end of March, Asian spot prices were running around $15.50 per mmBtu.
The survey looks at samples of fixed prices for LNG sold to power companies and utilities, and excludes spot deals linked to benchmark prices such as the U.S. natural gas Henry Hub index.
The survey excludes prices for long-term, mid-term or short-term contracts.
The ministry said the average prices will only be announced each month when there are at least two deals reported that meet the survey's criterion.
The ministry also said it is releasing the spot average price to pave the way for an LNG futures contract that the Tokyo Commodities Exchange is looking to launch next year.
The next monthly survey will be released in late May. (Reporting by Osamu Tsukimori; Writing by Aaron Sheldrick; Editing by Tom Hogue)