SINGAPORE, Feb 23 (Reuters) - The Middle East crude market firmed up, with April differentials strengthening on swift cargo trade and thinning supplies. The Abu Dhabi benchmark grade, Murban, was pegged at a slight premium of 0-5 cents a barrel to the ADNOC official selling price. *OMAN ASSESSMENTS - April Oman traded on the DME was at a premium of $3.31 to Dubai swap quotes at 0830 GMT, using the settlement price for DME futures, the ICE one-minute marker for Singapore and the Brent-Dubai EFS as calculated by Reuters. * EFS - Front-month Brent/Dubai Exchange of Futures for Swaps (EFS) for April rose 56 cents from the previous session to $4.35 a barrel. * MARKET NEWS - An Iranian supertanker loaded with crude has made a rare journey to an anchorage point off the coast of an Indonesian island used for offshore sales and storage of oil. - Myanmar will launch a global tender for six onshore oil and gas blocks as the reforming Southeast Asian country seeks to tap more foreign investment from the West, two Yangon-based sources with direct knowledge of the deals told Reuters. - Saudi Arabia's concern is to keep the global oil market well supplied, its deputy oil minister said on Thursday, as top Asian crude buyers look to the world's biggest producer to make up for cuts in supplies from sanctions-hit Iran. - Japan may cut Iranian crude oil imports by a more-than-expected 20 percent as it seeks a waiver from U.S. sanctions, a newspaper reported on Thursday, a move which would spare its banks from a major blow but also boost its rising fuel import bill. - South Korean Finance Minister Bahk Jae-wan said on Thursday the country's talks with the United States on cutting crude oil imports from Iran under the U.S. sanctions policy were "going smoothly." *REFINERY MARGINS - Complex processing margins for Dubai in Singapore were around $6.76 per barrel, down from an average of the last five days of $7.98, according to Reuters data. Over the last year, the average margin has been around $8.20 per barrel. * CRACK SPREADS - Fuel oil's March crack gained 6 cents to a discount of $5.60 a barrel to Dubai crude. - Gas oil's March crack gained 15 cents to a premium of $16.15 a barrel to Dubai crude. - The naphtha CFR Japan front-month crack eased $1.46 cents to a discount of $7.63 a barrel to Brent. *OUTRIGHT PRICES - April ICE Brent was at $122.94 a barrel at 0830 GMT, up $1.21 from the same time a day earlier. - April Oman rose $0.67 to $121.30.

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