The U.S.-based rights group Human Rights Watch has accused Indonesia's security forces of torturing detainees in the province of Aceh, where Jakarta is struggling to put down a separatist rebellion. The accusations come at a delicate time: the chief of Indonesia's armed forces is in the United States for a meeting with the head of the U.S. Asia-Pacific military command.

In a report released Monday, Human Rights Watch accuses the Indonesian army and police of using electric shocks and rifle butts against suspected Acehnese separatists.

The separatist rebellion in Aceh is Asia's longest-running civil war. In the last quarter of a century, more than 13,000 people are estimated to have died, the bulk of them civilian victims of the government's attempts to quash the rebellion.

The military has placed the province off limits to journalists and outsiders. Human Rights Watch secretly interviewed 33 adults and two children who had been detained in prison in order to get their stories.

Sam Zarifi is the deputy director of the group's Asia Division.

"It seems clear that the Indonesian government has systematically used torture and serious abuses of prisoners in many cases to get confessions from them, often false confessions, that are then used as the basis of convictions for treason," said Mr. Zarifi.

Indonesia's government has routinely denied similar accusations about Aceh in the past. A spokesman said Monday the government was still studying the report in detail, but said that the authorities had been at pains to ensure that they adhered to international norms of human rights and civil liberties.

Indonesia's security forces have a brutal record, and many countries, including the United States and Britain, have some kind of limitations on cooperation with them. But Indonesia is now a key ally in the war against terror, and there is pressure to resume normal military relations.

The head of Indonesia's armed forces, General Endriartono Sutarto, is currently in the United States, where he is due to hold five days of meetings with the head of the U.S. Asia-Pacific command, Admiral Thomas B. Fargo.

The meetings are due to start Monday - the same day the Human Rights Watch report has been issued.

A spokesman for the U.S. embassy in Jakarta said the meeting was to "address mutual interests, including military security concerns".