The environment ministry late Friday announced the move, which also covers the Aegean islands of Patmos and Leros, as the capital city's water reserves have been falling by approximately 250 million cubic meters per year since 2022.

A ministry source told state agency ANA the decision "prioritises the implementation of critical infrastructure projects".

No restrictions on consumer consumption have been announced for the time being.

According to the Athens water supply and sewerage company (EYDAP), annual rainfall in Greece has decreased by approximately 25 percent in the past three years, evaporation has risen by 15 percent, and consumption is up around six percent.

Environment and Energy Minister Stavros Papastavrou told Skai TV on Friday that reserves for the greater Athens area are around 400 million cubic metres, with consumption at approximately 250 million cubic metres per year.

"There is no more room to postpone difficult decisions," the minister said.

"In areas where water consumption increases significantly due to tourism, greater attention and planning are needed to avoid situations in the summer that cannot be dealt with," he added.

According to ministry sources, scientific studies show that Greece is experiencing a period of persistent drought comparable only to a previous crisis in 1988-1994.

The Greek government last month had already announced plans to invest 2.5 billion euros ($2.9 billion) in water infrastructure projects over the next decade.

The plan includes diverting two tributaries of the River Achelous in western Greece, in addition to drilling and desalination projects.

The 500-million-euro Achelous tributary project is to be completed by 2029.

Another 150 projects worth over 320 million euros are currently underway in more than 40 islands, according to the environment ministry.