Saddam Hussein was last night reported to have placed his defence minister and close relative under house arrest in an extraordinary move apparently designed to prevent a coup. Iraqi opposition newspapers, citing sources in Baghdad, yesterday claimed that the head of the Iraqi military, Lieutenant-General Sultan Hashim Ahmad al-Jabburi Tai, was now effectively a prisoner in his home in the capital.

The minister's apparent detention, also reported by Cairo-based al-Ahram newspaper, is surprising. He is not only a member of President Saddam's inner circle, but also a close relative by marriage. His daughter is married to Qusay Hussein, the dictator's 36-year-old younger son - considered by many as his heir apparent.

Reports of the general's arrest came amid signs of growing apprehension in Baghdad that the Iraqi army, including the elite Republican Guard, might desert in the event of an attack on Iraq.

Last night one independent source in Baghdad contacted by the Guardian confirmed that Gen Sultan was in custody. "He continues to attend cabinet meetings and appear on Iraqi TV, so that everything seems normal," said the source, a high-ranking official with connections to Iraq's ruling Ba'ath party. "But in reality his house and family are surrounded by Saddam's personal guards. They are there so he can't flee."

The source also claimed that several other high-ranking military and government officials had been arrested in the past few days. Any signs of dissent within Baghdad will be watched very closely by US and other intelligence services.

The fear that Iraq's 700,000-strong regular army might refuse to fight invading American troops has prompted President Saddam to take drastic measures. Last week he reportedly deployed a ruthless militia of Iranian fighters to several key cities to crush any popular uprisings. The Mojahedin-e-Khalq - a violent Iranian opposition group based in Iraq - was sent to defend urban areas, including Baghdad, Kurdish newspapers reported. MEK fighters have also arrived at the border with Kuwait and Syria.

The MEK remains fanatically loyal to the president and is likely to lead any street fighting against US troops, Iraqi opposition sources believe.