JAKARTA, July 10 (Reuters) - The European Commission is concerned about the lack of access to Indonesia's war-torn Aceh province since one of its aid workers was detained by immigration authorities, a diplomat said on Thursday.
EC political counsellor in Jakarta Ulrich Eckle said Belgian aid worker Karin Michotte was taken into custody when she arrived in Aceh on Tuesday and held overnight even though she had obtained permission from the government to visit the province.
He said Michotte was released on Wednesday and left Banda Aceh, the capital of Aceh, on Thursday for Jakarta.
An immigration official denied Michotte -- based in Thailand for the EU's humanitarian aid office -- had been detained.
"No, there was no detainment. What happened was that she was told to arrange a letter from the Ministry of Justice," spokesman Ade Dachlan told Reuters in Jakarta.
Eckle said Michotte, who he added was also questioned by the military, was treated in a "polite" manner and her cell door left open during her detention but the issue raised serious questions about access to the province where government troops launched a fresh offensive against separatist rebels in May.
"We are worried about access," Eckle said.
"We are more worried about the general aspect that this incident reflects how difficult it is to get the authority from this hierarchy and the government to reach this place and do normal humanitarian work," he added.
"The rules always change. It seems that very often the local authorities make their own rules and in Jakarta there may be some other rule -- it's really quite confusing."
The incident comes amid mounting concern expressed by rights groups over the government's efforts to restrict foreigners' entry to Aceh, which they say could open the way to abuses.
Curbs on foreign media reporting of the war have also drawn condemnation. An American freelance reporter was arrested last month in Aceh over immigration offences and could face trial.
Government troops and Free Aceh Movement (GAM) rebels have been fighting since 1976 but the military launched a fresh offensive on May 19 after peace talks with GAM collapsed.
The military has said more than 400 people, mostly rebels, have been killed in the latest fighting.