Prof Chowdhury, who is also the president of Bikalpa Dhara Bangladesh, alleged that somebody deliberately set fire to the house. He branded the incident as "a plot to assassinate me and my whole family."

He suspects that the ruling party men 'who have been carrying out repeated attacks on Bikalpa Dhara since its launching' are behind the attack.

The former president demanded a judicial probe into the incident by a sitting High Court judge.

Firefighters, however, failed to ascertain the reason of the fire.

Policemen who were guarding the house said they did not see anyone setting fire or running away from the scene.

The fire burnt two chairs in the northern part and another in the western part of the house, all the curtains and books and other papers in the drawing room were also burnt. The heat melted the air-conditioners on the ground floor and first floor and plastic paint coating on the walls.

The fire in the first floor bedroom burnt documents, books, other papers, clothes, carpet and foreign and local currencies.

Prof Chowdhury's family said the fire caused a loss of valuables worth Tk 4 to 5 lakh.

The fire was first noticed around 5:05am yesterday. "I saw the curtain at the northern side of the ground-floor drawing room burning and immediately phoned their domestic help, Jyotsna, who was sleeping inside," said an on-duty police constable, Masud, who was then sitting near the gate of the house 'Mayabi' on Road No 12 in Baridhara diplomatic enclave.

Jyotsna immediately knocked on the bedroom door of former president's son, Mahi B Chowdhury, on the second-floor of the three-storey building.

"Hearing screams, my wife Ashfa Haq Lopa woke me up. I opened my window to see smoke all around," Mahi told this correspondent. As he opened the door, he saw dense toxic smoke had covered the whole house.

"I brought my daughter Sherejad and son Arash Talesh who were struggling to breathe in the adjacent room to my room and rushed to recover my father from the first floor."

Mahi said he saw the drawing room and a first floor bedroom burning. "It was so hot that I felt like I was inside an oven."

He brought his father and mother, Hasina Warda Chowdhury, to his bedroom and came down with his family members before the blaze could reach his room.

Informed by the on duty police, Hamid, the supervisor of four police constables who guard the house in three-hour rotation shifts, and three other constables brought plastic pipes from an under-construction building just west to Chowdhury's house and poured water to douse the fire.

A Rab-1 patrol car that was passing by the house informed the fire brigade that reached few minutes after the policemen and three domestic helps brought the fire under control.

Mahi said they suspect the arsonists set the fire through two windows on the ground floor and through a window and a ventilator of the toilet on the first floor. "Most of the damage are beside the windows and the windowpanes are broken. The attackers used the see-saw as a ladder to set fire on the first floor."

Mahi and his wife told reporters that they smelt toxic gas during the fire and they were feeling itchy, which indicated that the fire did not originate from any electric short circuit.

"Experts said there is smell of phosphorus and that gunpowder have been used," Mahi told reporters.

During a news briefing later in the afternoon, Mahi said, "There is no doubt that it is an attempt to kill the former president with all his family members in a planned way."

"The fire didn't originate from a short circuit because my television was on during the incident and the constable phoned from the intercom. It also didn't originate from the gas stove because nothing was gutted in the kitchen," he said.

Prof Chowdhury said the attack was made to reap political benefit. "I don't have personal enmity with anyone. But Bikalpa Dhara men have been targets of ruling party attacks since our launching and we've been attacked almost everywhere when we organised any meeting or rally."

"The government might carry out more heinous attacks on us and this incident has strengthened that apprehension," he said demanding a judicial probe.

He said they had received phone calls and letters earlier threatening to kill him and his son.

Eminent jurist Dr Kamal Hossain, Nazibul Bashar Maijbhandari, Krishak Sramik Janata League chief Kader Siddiqui, Dhaka Metropolitan Police Commissioner SM Mizanur Rahman visited the spot.

Terming the attack a planned one that is of very grave concern, Dr Kamal expressed his surprise about how the attackers could escape despite the presence of five policemen.

He called for bringing in international experts and for an in-depth probe immediately. "The attackers have expressed the reaction of those who do not like his (B Chowdhury's) politics."

Fire Brigade formed a three-member departmental committee headed by Deputy Director (Operations) Selim Newaz Bhuiyan. It will submit a report in three days.

Visiting the house, the committee examined the burnt objects, electric cables, gas lines, and collected evidence.

Declining to make any comment on the cause of the fire, Selim Bhuiyan told The Daily Star, "We'll first examine the evidence, talk with experts and sit later to determine the cause."

About the possibility of an electric short circuit, he said: "We've found a break in the (electric) circuit, but it cannot be identified as the cause of the fire."