CAIRO (Reuters) - Egypt executed prominent Islamist fighter Adel Habara on Thursday, state media said, days after a top court rejected his final appeal and in defiance of militant threats to ignite “a volcano of jihad” across the country.

FILE PHOTO - The caskets of 25 policemen killed early Monday morning near the north Sinai town of Rafah lay on the ground after arriving at Almaza military airport in Cairo August 19, 2013. REUTERS/Mohamed Abd El Ghany

Habara, 40, was sentenced to death in 2014 for killing 25 army conscripts in Northern Sinai in August 2013. He was hanged early on Thursday after President Abdel Fattah al-Sisi signed off on the death sentence, state news agency MENA said.

Sisi has launched a fierce crackdown on Islamists since as Egypt’s then-military chief he overthrew the country’s democratically elected president, Mohamed Mursi of the Muslim Brotherhood, in July 2013.

He is battling a raging insurgency in Northern Sinai, led by Sinai Province, the Egyptian affiliate of Islamic State. The militant group has killed hundreds of soldiers and police in regular attacks that have intensified since Sisi took power.

After Habara’s appeal was rejected by the Court of Cassation on Saturday, Islamic State supporters issued warnings to Sisi online not to carry out the execution.

“To the tyrant Sisi, if you dare to execute Sheikh Adel Habara then, by God, you will have ignited a volcano of jihad all over the country and opened the doors of hell on your soldiers and dogs and institutions,” read a message on the Lone Wolves account run by Islamic State supporters on Telegram.

Though Islamic State attacks have largely been focused on security forces in its stronghold of Northern Sinai, a strategic area bordering Israel, Gaza and the Suez Canal, the group has also launched deadly attacks in Cairo.

Islamic State claimed responsibility for a suicide bombing at the country’s main cathedral that killed 25 people on Sunday.

It also said it had brought down a Russian airliner last year, in an attack that killed 224 people and dealt a blow to the tourism sector, by planting a bomb in a soft-drink can.

MENA said Habara had been taken from his cell at the maximum security Aqrab, or Scorpion, jail in Cairo to the Court of Cassation, where he was hanged in the presence of judicial officials.