Protesters fear job losses because the governing Syriza party has fought the mine on environmental and financial grounds.
The mine is owned by a subsidiary of Eldorado Gold Corp. (TSX:ELD), a Vancouver-based company listed on the Toronto and New York stock exchanges.
Eldorado said last month that it believed there was no legal basis for the ministry responsible for environment and development to revoke permission to complete construction of a key ore enrichment plant at the Skouries mine.
The government has accused the mining company of encouraging the protests.
Police closed major roads as miners marched on Thursday to the development ministry Thursday, where they shouted slogans and banged their hard hats on the ground.
— With a file from The Canadian PressSuggest a correction