SANTIAGO, Chile, March 5, 2012 � Orosur Mining Inc. (the "Company") (TSX VENTURE: OMI) (LSE: OMI) a South American-focused gold producer and explorer, today announces that it has commenced drilling on its 100 per cent owned Mahoma Project in Uruguay. A programme of approximately 3,000 drill metres comprising 2,000 metres of RC pre-collars and 1,000 metres of diamond drilling is planned.

Orosur has held the property since 2009, however, issues with land access had previously prevented exploration.  During the second half of 2011, these issues were resolved and exploration can now be conducted.

The Mahoma Project, previously operated by American Resource Corporation, produced 16,419 ounces (73,431 tonnes at 6.98 g/t Au with 91.6 per cent recovery) between 1993 and 1997. A pre-mining non -compliant NI 43-101 probable reserve of 281,000 tonnes at a diluted grade of 9.36 g/t (15per cent dilution assumed) was estimated by Watts, Griffis and McOuat.

David Fowler, CEO of Orosur commented:

�We are pleased to have commenced drilling at the high grade Mahoma vein system in Uruguay. With a historical non NI43-101 compliant reserve of 281,000 tonnes at a grade 9.36 g/t au and significant exploration upside, we believe that Mahoma could ultimately deliver an increase in Orosur�s Uruguayan production by 25,000 to 30,000 ounces per annum with minimal capital�.

The Project area contains four principal gold bearing quartz veins that were previously mined via shallow open pits within granodiorite host rocks. The area is located approximately 130 kilometres from Montevideo and 405 kilometres from the San Gregorio mine in the Florida Greenstone belt. This belt is approximately 15 km wide by 150 km long.  The granodiorite measures approximately 3 km wide in the Mahoma area and contains additional quartz veins that have not yet been explored.

The four principal veins have been identified as veins I, II, IIB and IV. The II vein is the longest and most consistent that has been historically drilled and mined. It has a drilled strike length of 900 metres and a shallow open pit along 450 metres of its strike length. The main portion of Vein II is subvertical and the average true thickness is around 1.7 metres.  A second portion of the II vein is approximately 1,200 metres to the east of the main mineralized lens and it has been drilled for over 700 metres of strike with 220 metres showing continuous mineralization. The width of the second vein varies from 0.2 metres to 3.2 metres with an average width of approximately 1.9 metres.

Vein IIB, 300 metres to the south of the II vein, is approximately 550 metres in length and exhibits an average width of 1.5 metres.Vein IV is a thicker quartz vein zone than the other zones but also has a lower grade and a shorter strike length of approximately 250 metres. It has only been drilled to only 30 metres from the surface. Vein I comprises  a series of short and narrow veins with the average width of these veins being 20 centimetres and the largest vein having a strike length of 100 metres.

Only the upper portions of the four drill hole defined veins have previously been mined and there is significant exploration upside potential to define more veins and extend the known veins down dip.

Orosur�s initial drill programme is designed to confirm historical drill results for vein II, vein IIB and vein I. This work is expected to be followed by infill drilling to target an initial measured and indicated resource of 250,000 tonnes. If this programme is successful a feasibility study to develop an underground operation producing 25,000 to 30,000 ounces per annum is planned.

This study is likely to be based on ore being trucked to the San Gregorio mine thereby limiting capital expenditure on processing plant and simplify permitting as no cyanide will be used at the site.

Qualified Person's Statement

The information presented in this press release has been reviewed by William F. Lindqvist, a director of OMI. Dr. Lindqvist holds a Ph.D. in Applied Geology from Imperial College, London, has been a member of the AusIMM for 46 years, and has had 40 years of experience in international minerals exploration and property evaluation.

Forward Looking Statements

All statements, other than statements of historical fact, contained or incorporated by reference in this news release, including any information as to the future financial or operating performance of the Company, constitute �forward-looking statements� within the meaning of certain securities laws, including the �safe harbour� provisions of the Securities Act (Ontario) and the United States Private Securities Litigation Reform Act of 1995 and are based on expectations estimates and projections as of the date of this news release. There can be no assurance that such statements will prove to be accurate, such statements are subject to significant risks and uncertainties, and actual results and future events could differ materially from those anticipated in such statements. Forward-looking statements include, without limitation success of exploration activities; permitting time lines; the failure of plant; equipment or processes to operate as anticipated; accidents; labour disputes; requirements for additional capital title disputes or claims and limitations on insurance coverage. The Company disclaims any intention or obligation to update or revise any forward looking statements whether as a result of new information, future events and such forward-looking statements, except to the extent required by applicable law.

ENDS

Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.

About Orosur Mining Inc. 

Orosur Mining Inc. is a fully integrated gold producer and exploration company focused on identifying and developing gold projects in Latin America. The Company operates the only producing gold mine in Uruguay (San Gregorio), and has assembled an exploration portfolio of high quality assets in Uruguay and Chile. The Company is quoted in Canada (TSX-Venture Exchange: OMI) and London (AIM: OMI).

For further information, please contact:

Orosur Mining Inc
David Fowler, CEO
Ignacio Salazar, CFO  + 56 2 9246800; info@orosur.ca

Canaccord Genuity Limited (Nominated Adviser & Broker)
+44 (0) 20 7050 6500
Rob Collins
Bhavesh Patel

Blythe Weigh Communications (Investor Relations)
Tim Blythe: +44 (0) 7816 924626
Matthew Neal: +44 (0) 7917 800011