KHARTOUM (Reuters) - Sudan has arrested three Sudanese suspected of helping to kidnap a French/British Red Cross worker in Darfur, security and aid sources said on Tuesday.

Gauthier Lefevre was the fifth expatriate humanitarian worker to be kidnapped in Sudan since the International Criminal Court issued an arrest warrant for President Omar al-Bashir in March, accusing him of war crimes in western Sudan.

"We have arrested three people ... Sudanese ... and they are under interrogation," a senior official in Sudan's intelligence forces told Reuters on condition of anonymity.

He said the three were accused of helping to plan the kidnapping and were being held in the West Darfur capital el-Geneina.

Another security source said one of those detained was a woman, accused of letting the kidnappers stay at her home.

The International Committee for the Red Cross (ICRC), which suspended operations in West Darfur after Lefevre's abduction, said it had no information on the detentions.

"The ICRC trusts that the authorities are taking all measures to ensure a smooth release," said ICRC spokeswoman Tamara al-Rifai.

Aid workers fear further abductions as Khartoum has not caught any of the kidnappers despite knowing their identities. Reports of ransoms being paid for those released have encouraged more kidnappings, they say.