Hundreds of bonfires dotted the Baltic Sea coast of Estonia Saturday night, a centuries-old maritime tradition to guide seafarers now celebrated with a tech-savvy environmental twist.

Summer revellers from as far as Finland, Sweden, Latvia and Russia also signed up to be part of the event on the interactive Ancient Bonfires website http://www.ancientlights.eu/ set up by Mairold Vaik.

The popular Estonian blogger told AFP that while the site registered hundreds of hits this year, he aims to close a ring of bonfires around the Baltic Sea by 2018, all in a bid to draw attention to its serious environmental challenges.

According to the World Wildlife Fund, the Baltic is one of the most threatened marine ecosystems on the planet.

Scientists say that the shallow and closed body of water is particularly vulnerable to overfishing and agricultural fertilisers.

Once washed into the sea, nitrate and phosphate-rich farm run-off triggers oxygen-depleted zones where no marine life can exist.

Encircled by nine countries, including Estonia, Denmark, Finland, Germany, Latvia, Lithuania, Poland, Russia and Sweden, the Baltic has an estimated 16 million people living along its shores.

"We hope that people in other Baltic Sea states like Denmark, Germany, Lithuania and Poland will join us in the coming years," Vaik told AFP.