(REUTERS) -- Indonesia will ban exports of some unprocessed metals from 2014 and could revoke the export licences of firms that violate the ban, the energy ministry said in a regulation that was posted on its website on Friday but later disappeared.

The regulation was visible on the ministry's website on Friday but by evening it could no longer be seen, leaving its status unclear.

Minerals covered by the ban, which has been widely discussed, include copper, gold, silver, nickel, tin, bauxite and zinc. Coal will be regulated separately.

Mining license holders that started their operations before the regulation was announced must meet the minimum processing requirements within five years after the 2009 Mining and Coal Law was introduced, said one of the articles in the regulation.

The regulation would improve domestic metal production capacity, boost supplies of refined products to the domestic market and increase government revenue, the ministry said.

Indonesia is Southeast Asia's largest economy and a major global producer of raw materials. The Indonesian Mining Association has urged the government to delay the regulation's implementation, particularly with respect to coal.

By about 6.45 local time (1145 GMT), the regulation could no longer be seen on the ministry's website.

The regulation is an extention from the 2009 mining and coal law and what is stated there is valid. However, I didn't know that the regulation had been issued and I had no idea that it has been removed from the website, deputy energy minister Widjojono Partowidagdo told Reuters by telephone.

Earlier on Friday, the association's chairman, Bob Kamandanu, said the regulation as it stood was acceptable.

Minerals like gold and tin need to be processed anyway so the mining companies do not have to make a big overhaul to meet the regulations. However, for coal, that's another story, he told Reuters.