MADRID, Nov 29 (Reuters) - About one third of Spanish pork export certificates have been blocked after the first outbreak ​of swine fever for three decades, Spain's agriculture minister said ‌on Saturday.

"Of the 400 export certificates to 104 countries, a third are blocked. We ‌are working to open them as quickly as possible," Agriculture Minister Luis Planas told a press conference.

The virus, last recorded in Spain in 1994, was detected in six wild boar near Barcelona.

Planas said the value of the country's ⁠pork exports is 8.8 ‌billion euros ($10.20 billion), of which 58% goes to the European Union.

He said exports to the ‍EU were not affected except those which fell within a 20-kilometre zone near the source of the outbreak.

"Our task is to keep international markets open," he added.​

Spain's northeastern region of Catalonia has barred access to a major natural park ‌after six wild boar found dead near Barcelona tested positive for African swine fever.

The Collserola park was closed for all leisure activities and outdoor activities were restricted in 60 villages near the centre of the outbreak, the Catalan Agriculture Ministry said late on Friday.

Catalan authorities will deploy traps for wild boar and deploy police to enforce ⁠barriers to the area.

African swine fever is not ​harmful to humans but spreads rapidly among pigs ​and wild boar.

Taiwan was the latest country to announce restrictions on Spanish pork imports, when its agriculture ministry said on Saturday it ‍had banned all pork ⁠products and live pig imports.

China has banned pork imports from Barcelona province, a Chinese Customs document seen by Reuters showed.

Britain on Friday said ⁠it would temporarily stop imports of pork meat from Catalonia. Mexico has suspended imports of pork products ‌from Spain.

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(Reporting by Graham Keeley, ‌Editing by Timothy Heritage, Kirsten Donovan)