Two members of Médecins Sans Frontières have returned to Baghdad after being arrested and held for eight days by Iraqi secret police, accused of being spies. François Callas and Ibrahim Younous were kept in some of the regime's most notorious prisons before being dumped on the streets in the city of Ramadi, in western Iraq, on Friday evening.

The two men were among dozens of foreigners who were picked up by the Mukhabarat, the Iraqi secret police, in the dying days of Saddam Hussein's regime and then disappeared into the netherworld of the security apparatus while Baghdad fell to US forces.

Mr Callas, 43, from Paris, and Mr Younous, 30, who is originally from Sudan but now lives near Leicester, revealed details of the arbitrary way foreigners were detained in Baghdad as the Iraqi regime hunted for American and British agents.

A Japanese journalist on a taxi ride was taken by the driver to the Mukhabarat headquarters because it was claimed he shot unauthorised film on his video camera. Others were picked up merely on suspicion. The experience of the two medical aid agency officials also shows that cities such as Ramadi, an important administrative centre for western Iraq which is behind American lines, remain in the hands of the regime's officials.

The aid workers were arrested in their rooms at Baghdad's Albraj Hotel after the secret police were informed that they had been using a type of hand-held satellite telephone banned by the regime. They were first taken to Abu Gharb, a vast jail in the suburbs of the capital, and from there to prisons in Falluja and Ramadi. Around 100 detainees, including local prisoners, were put in a cell meant to hold around 20 in Ramadi.

At Falluja there was just one toilet and one water point for 200 people. Although the agency men were not physically mistreated, they did hear other prisoners being beaten. Their belongings, including passports and $25,000 in cash, have disappeared. While the foreign prisoners were held at Abu Gharb, the area came under attack from the Americans. "It was very worrying," said Mr Callas.

"There was an anti-aircraft battery that kept firing away from the top of the building, and there was the obvious possibility that we were going to be bombed. All the guards hid in the bunker, so there was no one to do anything even if we had been hit." Mr Younous said: "The conditions were appalling.

The food, when we had it, was terrible. One of the main problems was that with the war, telephone links had broken down between Baghdad and other areas. The intelligence people did not know what to do with us, and because of the nature of the system here, no one wanted to take responsibility.

"We were evacuated from Abu Gharb and Falluja because it simply got too dangerous for the Iraqis who were holding us. When we got to Ramadi, the police chief there did not want the responsibility of having us in his custody. But, at the end, they had nowhere else to put us."

Mr Callas and Mr Younous said the scale of abuse depended on the type of alleged crimes of those arrested and their nationality. Political prisoners - Iraqis and Arabs among the foreigners - suffered the most.