LONDON (AP) _ Fears of an al-Qaida terrorist attack prompted Queen Elizabeth II to install ``panic rooms'' at Buckingham Palace and Windsor Castle, a newspaper reported Sunday.

The high-security rooms are encased in 18-inch-thick steel walls and are designed to protect senior members of the royal family from poison gas, bomb attacks or assassination by terrorists, The Sunday Times reported.

The shell of each room is bullet-resistant and fire-retardant, and the rooms themselves could withstand a mortar attack and possibly a direct hit by a light aircraft, the newspaper said.

Windsor Castle lies on the flight path for London's Heathrow Airport.

The rooms are equipped with secure communications, beds and washing facilities, and are stocked with enough food and hot water for the royals to survive at least a week, the newspaper said.

The new rooms were built following a security review after the Sept. 11 terror attacks in the United States, the newspaper said. They cost $1.6 million and replaced smaller, sparsely furnished rooms.

Buckingham Palace did not immediately return calls late Saturday.