Mothafar Assar's spell in the limelight lasted only 30 minutes before the Hamas security forces came to break up his inaugural gig.

A crowd of 450 people had crammed into the hotel venue for Gaza's first rap party, scheduled to last for three hours. As the audience left, the police confiscated video cameras, returning them later with the subversive images of Assar's Street Band Rappers removed.

Assar was bitterly disappointed but not surprised. He had been running around until 3am that morning trying to secure a licence for the gig from authorities, who first raised concerns that the audience would be mixed and then said the music was haram (forbidden).

"They were giving me any excuse," he said, adding that even his appearance at the time – shaved head and sculpted beard, unusual in Gaza – counted against him.

The party, in March 2009, was intended to mark a new peak in Assar's burgeoning rap career. Having fallen in love with the music of rappers such as 50 Cent at the age of 13, he was fulfilling a dream to perform Arabic rap to a home audience in Gaza.

"When I started listening to rap, I had no idea that there was Arabic rap," he said at his home near Nuseirat, where his bedroom is decorated with rap graffiti. It took him three years to stumble across an Algerian rapper, at which point he thought: "Why shouldn't I do this?"

Alone he began to write lyrics, although "it wasn't easy to get the tempo right". Things picked up when he teamed up with another rap devotee, Salim. "We were trying to develop our skills, composing our own melodies and lyrics, teaching ourselves off the internet."

The pair sought sponsorship from various NGOs in Gaza to no avail until the French Cultural Centre offered to help. Things were looking up, and then a bloody battle erupted between Hamas and Fatah which resulted in Hamas seizing total control of Gaza.

A friend of Assar's was killed in the fighting, inspiring the young rapper to write his "most powerful" song to date, called Ya Allah (My God), with references to pain, loss and the need for unity.

The Street Band Rappers, consisting of Assar and two co-performers, were invited to appear at various Gaza parties as part of a wider musical line-up, gaining the confidence and experience to organise their own ill-fated gig 18 months ago.

Life since then has not been easy. "We haven't tried to organise any more of our own parties," he said. Studio owners have been discouraged from permitting the band to record, putting a 12-song album on hold. The authorities have advised those organising private parties to remove the Street Band Rappers from the line-up if they wish to be granted a licence. There is no prospect of financial sponsorship.

Almost his only offer came from the Israeli rights group Peace Now, which urged him to record a track with an Israeli rapper to promote co-existence. Assar wrote some lyrics but then reconsidered his involvement. "I believe it could have been a positive thing, but I would have been viewed as a collaborator. I would have been arrested the next day."

At one point there were three rap bands in Gaza, said Assar. That whittled down to the three-man Street Band Rappers, who then lost a member. Salim, Assar's remaining partner, is now abroad, leaving the 23-year-old as the last rapper in Gaza.

"Hamas is not happy with this type of music," said Assar, explaining that it is the westernised form of the genre, rather than the lyrics, that the Islamic organisation finds unacceptable. "I'm very disappointed. All I'm asking for is a space to work and perform. The only choices I have are to stop rapping or leave Gaza" – which, he acknowledges, is not easy.

The lack of freedom of expression is hard, not just for Assar, but for many young Gazans who cannot channel their dreams, emotions and frustrations through music, unlike youth in most parts of the world.

For now, Assar is just about keeping his dream afloat. "I have a message and I want it to reach as many people as possible. Actually it's not just one message, it's about everything in Gaza. It's not just about the [Israeli] occupation, it's about the occupation of our minds."