JAKARTA, Feb 27, Reuter - Indonesia will begin the trials next week of 18 people charged with subversion for their part in a rebellion in Sumatra's Aceh province.

The subversion charges appear to contradict repeated government claims that rebels who say they are fighting to free the fiercely Islamic province from Jakarta rule are nothing more than common criminals with no political motives.

A spokesman at the state prosecutor's office in Banda Aceh told Reuters by telephone on Wednesday the trials would be in three cities in Aceh and neighbouring North Sumatra.

"Of course they will be tried for subversion, that's perfectly clear," he said.

Rebels calling themselves the Aceh Sumatra Liberation Front have led an 18-month insurgency.

Jakarta sent some 14,000 troops into trouble areas according to military sources. Civilians complain of brutality by troops and rebels.

A military doctor said at the height of the conflict in November that over 1,000 people had been killed.

Sources in Banda Aceh said the violence was lessening. They said rebels killed two people this week and several school buildings, including an Islamic boarding school, had been set on fire.

The official Antara news agency on Tuesday quoted a Banda Aceh police official as saying rebels had torched 12 educational institutions, including a university, in the last eight months.

Independent political observers in Banda Aceh said they thought it unlikely the rebels would do anything so unpopular.

"An Islamic school, imagine! They are not so stupid. Everyone here believes it is the other side (the military) doing it to try and discredit the rebels," said one.

"Apart from anything else, the worthy soldiers are out there the very next day conspicuously rebuilding the school." He said such tactics were common. "And we will see a lot more of this as the trials go on."

Hundreds have been arrested during the rebellion. Many were quickly released but some are being detained indefinitely with no information given to their families.

The prosecutor's office spokesman would not give the names of those to be tried. Local sources said they expected one or two intellectual masterminds to be included in a batch dominated by gun-toting front-line rebels.

Antara reported on Wednesday that two Islamic religious figures had abandoned the rebels and turned themselves in to the Aceh authorities.