A university student and fan of breakdancing who worked part-time to fund his studies, Seifeddine Rezgui seemed like a normal young Tunisian man.

So when the 23-year-old was identified as the jihadist gunman behind Friday's massacre of 38 people at a seaside resort, many of his countrymen were left in shock.

In his hometown of Gaafour, a small city in northwestern Tunisia, friends and family painted a picture of a law-abiding young man who seemed far removed from a jihadist fanatic.

His cousin Nizar told AFP that just the day before the attack he had seen Rezgui in Gaafour, where the young man would return to work as a waiter to finance his studies for a master's degree at a technical institute in central Tunisia.

"He was normal. He came here, he worked in the cafe, he went home, he went to pray and he hung out with the guys at the cafe," said Nizar, 32.

"All Gaafour was surprised."

Tunisian authorities have admitted that Rezgui was not on their radar, saying there were no indications that he could be planning such an attack.

"He was unknown to our services. His family environment was normal," ministry spokesman Mohamed Ali Aroui told private television channel El Hiwar Ettounsi.

In a report on Rezgui, the channel branded him the "enigmatic terrorist", asking: "How does a university graduate go from being a young man who succeeds in his studies to becoming a terrorist and killer of innocent people?"

At the tiny family home in Gaafour's poor neighbourhood of Hay Ezzouhour, visitors have been expressing their condolences to Rezgui's devastated father.

Approached by reporters, he wearily turned them away, saying: "Please, don't talk to me."

Like many others in the neighbourhood, Rezgui's uncle Ali, 71, said he was shocked.

"In 23 years, he never did anything illegal. He finished his classes, he laughed, he'd say hello and go on his way," he told AFP.

"How did he train? Where did he train? Only God knows. This is what is tormenting us right now," Ali said.

Many of those who knew Rezgui said he seemed not at all like a "soldier of the caliphate" -- as he was dubbed by the Islamic State group when it claimed responsibility for the attack.

A young man from Gaafour said he had met Rezgui at a local youth centre dance club.

"He was a really good breakdancer," he told AFP, speaking on condition of anonymity as he feared he would be suspected of links to the attacker.

Tunisian media have aired a video from 2010 showing a young man breakdancing in a cap and identifying him as Rezgui.

Interviewed by Tunisian media, several of his neighbours in Kairouan, where he studied at the Higher Institute of Technological Studies (ISET), said they had not noticed anything unusual.

But, according to the interior ministry, Rezgui had been isolating himself in the lead-up to the attack.

"Recently his companions noticed a kind of rigorousness in him and that he was developing a tendency for solitude," Aroui said.

"He threw himself into the Internet and didn't even want to show his friends what he was surfing. He would isolate himself when he went on the Internet."

Security sources told AFP there was no record of Rezgui travelling to Libya, where some jihadists have pledged allegiance to IS, but said that he may have crossed into the chaos-wracked country illegally.