Pro-Gaddaffi forces have been seen roaming the streets of Misurata wearing gas masks, contacts in Libya's besieged city have reported to timesofmalta.com .

Sources at the hospital confirmed that pro regime troops were wearing gas masks. An independent source said there were reports that thousands of gas masks had been distributed to troops yesterday.

The news comes in the wake of an announcement by the Gaddafi regime that a NATO air strike last night had killed Muammar Gaddafi's youngest son, 29-year-old Saif al-Arab and three young grandchildren.

Libyan officials took journalists to the house, which had been hit by at least three missiles. The roof had completely caved in at places, leaving mangled rods of steel hanging down among splintered chunks of concrete.

The information raises the prospect of use of chemical weapons, long feared to be in the possession of the Gaddafi regime.

A source in touch with civilians on the ground said:

"The winds are blowing from the East right now which would make a gas attack unlikely but many people are viewing the death of Gaddafi's son as the tipping point which could trigger the worst feared retaliation."