Fakhruddin Kasem hoped for a prosperous new life when Indonesia struck a deal to end a separatist conflict in Aceh, but a decade on the unemployed former rebel is so desperate he hopes to join the Islamic State group to make ends meet.

While many ex-fighters have benefited from peace in the western Indonesian province, with ex-rebels now Aceh's key political players, former local commander Kasem is among a number that feel let down.

"As a rebel fighter, I feel betrayed by the leadership as they have not taken care of me," said the 35-year-old, one of about 100 ex-rebels who pledged last month to join IS in Syria as they claim being salaried jihadists is the only way they can support their families.

Up to 500 nationals from Indonesia, the world's most populous Muslim-majority country, are believed to have travelled to the Middle East to join IS, sparking fears they could revive sophisticated militant networks responsible for attacks on Western targets on their return.

It is not clear whether the ex-rebels will really join the fight in Syria and Iraq, but the threat highlights how the transition to civilian life for many Free Aceh Movement (GAM) rebels has not always been smooth.

In 1976, GAM launched its fight for an independent Islamic state in Aceh, which is fiercely proud of its identity and was historically an important trading centre and seat of Muslim learning.

Over the next 29 years, fighting between rebels and Indonesian government forces left about 15,000 people dead -- with abuses committed by both sides -- before the 2004 tsunami finally persuaded GAM and Jakarta to strike a peace deal.

The destructive, quake-triggered waves left around 170,000 dead in Indonesia, the vast majority in Aceh, and tens of thousands more in countries around the Indian Ocean.

The deal was signed on August 15, 2005, in the Finnish capital Helsinki, with the rebels agreeing to give up their demands for independence in exchange for greater autonomy.

The GAM fighters laid down their arms and Jakarta withdrew non-local security forces from Aceh and granted an amnesty to rebels and political prisoners.

A transitional reintegration package from the International Organization for Migration was provided to 2,000 prisoners who were granted amnesties and 3,000 former combatants, while ex-rebels have been brought into local politics and now lead the province.

- 'Many challenges' -

Despite sporadic violence, often between new local political parties set up as part of the peace deal, the accord has largely been viewed as a success, Aceh is mostly peaceful, and the chances of a return to full-blown conflict are slim.

But observers say that while some former GAM members have prospered in oil- and gas-rich Aceh, others have got very little, and those now in positions of power stand accused of being more interested in improving their own lot than helping ordinary Acehnese.

"The whole question of reintegration has been a problem from the start," said Keith Loveard, a senior risk analyst at Concord Consulting in Jakarta. "Some got involved and some were left out."

He pointed to high levels of crime in some parts of Aceh, which in many cases is suspected to involve former fighters, as evidence of failure.

One former rebel, Nurdin bin Ismail Amat, is leading an armed group that is suspected of being behind the kidnapping of a British energy worker in 2013 and the killing last year of two military intelligence officers.

He told AFP that he had decided to keep up the armed struggle as "we see the people of Aceh and former combatants have not prospered".

More broadly, critics say that governance in the province over the past decade has been ineffective, pointing to problems in the education system, rising infant mortality rates and growing drug problems.

The end of conflict also led to a dramatic increase in Islamic regulations in Aceh, the only province in Indonesia allowed to implement sharia law, with public canings common for crimes such as gambling and drinking alcohol.

In addition, not all elements of the peace deal have been implemented. In a 2013 report, Amnesty International noted promises to set up a human rights court and a truth and reconciliation commission had not been honoured, leaving many who suffered without a sense of closure.

Aceh governor Zaini Abdullah, himself a former rebel who used to be a key figure in the independence movement's government in exile, this week hailed "10 years of peace", but admitted problems remain.

"There are still many challenges," he told reporters.