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CARACAS, April 30 (Reuters) - Venezuela plans to halt work on at least two gold projects in a mineral rich jungle reserve, the miners said on Wednesday, in what could be the latest move by President Hugo Chavez against foreign companies.

Canadian miner Crystallex (KRY.TO: Quote, Profile, Research) said the environment ministry denied an exploration permit for its Las Cristinas project, which sits on what could be one of Latin America's largest gold deposits.

U.S.-based miner Gold Reserve (GRZ.TO: Quote, Profile, Research) also said the ministry had communicated a plan to rescind its permit to build its Brisas project, in the same Imataca reserve as Las Cristinas.

Both companies' stock value fell sharply on Wednesday.

"It is unfathomable that the ministry suddenly attacks mining projects in the Imataca," Gold Reserve President Doug Belanger said in a statement.

The environment ministry told Reuters it was not able to comment, while mining ministry officials said they had not been informed of the situation.

Several other mining companies are seeking permits in the Imataca reserve, which is home to several small indigenous groups and many small-scale unlicensed miners.

The Venezuelan move comes weeks after South American ally Ecuador suspended foreign mining companies' work in that country. Both leftist governments seek to control more of their economies amid a worldwide resource nationalism drive.

Chavez has nationalized large swathes of OPEC-member Venezuela's economy, including foreign-owned oil projects. In recent weeks he announced the takeover of the cement industry and the country's largest steelmaker.

The Imataca reserve in remote south eastern region of Venezuela is rich in minerals, timber and wildlife.

The companies said the communication from the government cited sensitivities surrounding indigenous peoples, small miners and the environment.

Belanger said Gold Reserve had already invested $300 million in Brisas and expected to spend $1 billion over the life of the mine, which he said would be the largest gold pit in the country.

Last year, Gold Reserve told Reuters the mine was set to open in 2010 and would produce 486,000 ounces of gold a year. Crystallex says Las Cristinas has proven and probable reserves of 17 million ounces.

Both companies said they would act vigorously to defend their interests in Venezuela. (Reporting by Frank Jack Daniel and Patricia Rondon in Caracas and Cameron French in Toronto; Editing by Christian Wiessner)