The student was “extremely intelligent” and lived in Plovdiv, Bulgaria’s second city, deputy prosecutor general Ivan Gueshev said, adding that this was the first investigation of its kind in the country.

“Several home-made explosive devices were found at his home, including a bomb made with pipes and electric wires (of a type) often used in the United States,” he said.

“Furthermore, 14.5 kg of the explosive used in attacks in Belgium and France, were found in a plastic container surrounded by nails to cause maximum destruction,” he added.

Gueshev did not identify the explosive but said it was the same as the one used in a 2012 attack on Israeli tourists at the airport in the Bulgarian Black Sea resort of Burgas, in which six people died and more than 30 were injured.

“This appears to be a classic case of the recruitment and radicalisation of a minor” on the Internet, he said.

An IS flag was also found in a room which was serving as the workshop.

The suspect had managed to make explosives from commonly accessed materials and that too in the space of a week, Gueshev said.

He did not say if the attack targeted Plovdiv, which is currently the European capital of culture and attracts many tourists.

The student has been released after arrest and is receiving counselling.

Bulgaria, which neighbours Turkey, is used by many jihadists to travel and return from the Middle East but no national has so far been caught for planning attacks on home soil.