A French woman kidnapped from Kenya by suspected Somali militants earlier this month has died, say French officials. Diplomats said they were told of Marie Dedieu's death by contacts through whom they had been negotiating her release. The exact date and circumstances of her death are not known, but her poor health and the fact medication had been withheld had led to fears this "tragic outcome was highly likely", they said. Mrs Dedieu, 66, was one of four Westerners recently taken from Kenya. In September, Briton David Tebbutt was killed and his wife Judith abducted from a luxury resort of Kiwayu on the Kenyan coast. Earlier this month, two female Spanish aid workers with the charity, Medecins Sans Frontieres (MSF) were seized from the Dadaab refugee camp near the Kenya-Somalia border. All three kidnapped women are still missing. Mrs Dedieu, who was a wheelchair-user and had to take regular medication for cancer and heart problems, had lived part-time in Kenya since the 1990s. She was taken from her beachfront home on the small island of Manda in the Lamu archipelago on 1 October by an armed gang. Officials confirmed she had been taken by sea to Somalia and that the kidnappers did not take her wheelchair or medication with them. In a statement, the French foreign ministry said expressed its "indignation at the total lack of humanity and the cruelty shown by the kidnappers of our compatriot". It demanded that those responsible be brought to justice. Kenya troops The finger of blame for the spate of kidnappings has been pointed by the Kenyan government at the al-Shabab Islamist militant group which controls most southern and central areas of Somalia. But Somalia has been wracked by fighting between various militias for two decades, so weapons are widely available and there are many armed groups who could be responsible. Correspondents say al-Shabab has not previously seized foreigners far from its own territory, while the numerous pirate gangs working out of Somalia normally kidnap ships and their crew for ransom rather than operating on land. Kenya has responded to the spate of kidnappings by sending troops into Somalia on Sunday to fight the militants. In a statement, MSF said it wanted to "firmly diassociate" itself from any military action aimed at freeing the Spanish doctors. "Abductions are extremely complex and need to be handled with care. Therefore, MSF is very concerned that security and the resolution of the incident could be compromised by any use of force being related to the case," MSF Spain head Jose Antonio Bastos said. He said MSF had no verifiable information on who was responsible for the abductions and what their motives were. "MSF is currently engaging with all relevant actors to seek the safe and swift release of our colleagues and any use of force could endanger this," Mr Bastos said. A Somali government general, Yusuf Dhumal, told the BBC Somali Service on Tuesday that his troops were with the Kenyan force heading towards an al-Shabab-held town of Afmadow, 120km (75 miles) from the border Reuters news agency reports that columns of al-Shabab battle-wagons mounted with heavy machine guns have rushed to reinforce Afmadow, which is about 90km north of the port city of Kismayo, al-Shabab's main economic power base. Al-Shabab has denied carrying out any abductions and has warned of attacks in Kenya unless the troops withdraw. The group, which has links with al-Qaeda, has threatened Kenya on several occasions in the past. But it has rarely acted outside Somalia - the only previous major attack it has said it carried out was a 2010 suicide bombing in Uganda's capital Kampala in which dozens of people died.