Almost all security measures agreed to by the government and the Pakistan People's Party for the homecoming of former premier Benazir Bhutto [Images] were compromised due to the massive turnout of her supporters.

A sea of humanity was waiting outside the Jinnah International Airport when a flight from Dubai brought Bhutto back from eight years in exile on Thursday and ensured that her motorcade did not leave the airport for almost 90 minutes after she landed.

Karachi Police Chief Azhar Farooqi, who was "perturbed over the disregard for security", said among the most obvious violations of the security plan was the breaking of the cordon by PPP supporters.

Another violation was Bhutto's decision not to use the bulletproof screen specially made by the PPP in consultation with the police, he was quoted as saying by the daily Dawn.

Though Bhutto was travelling in a truck that was specially modified for the occasion with the addition of armour plating, a bulletproof screen on its top was removed and dumped at the vehicle's rear at the PPP chairperson's request, the newspaper quoted sources close to the party as saying.

The PPP volunteers who formed a security ring around the truck, as it inched its way from the airport to the mausoleum of Pakistan's founder Muhammad Ali Jinnah, found it hard to keep away people who wanted to get close to Bhutto.

Some of the volunteers were seen pushing persons who clambered on to the truck to shake hands and have a word with Bhutto.

The standard operating procedures for Bhutto's security plan were breached by persons who climbed on to the truck to hand over bouquets to the former prime minister, the daily said.

A senior police officer said, "Perhaps the only reliable tool was the presence of two jammer-fitted" vehicles in the motorcade.

Authorities in Karachi deployed some 20,000 police and paramilitary personnel to protect Bhutto following threats by Taliban and Al Qaeda [Images] to kill her.

The PPP also mobilised 5,000 volunteers to form a security ring around her convoy.

Helicopters hovered over the city from the time her flight landed to keep an eye on her movements and deter possible attacks.

Despite the security arrangements, the motorcade was targeted by a grenade blast and a suicide bomber, killing 165 and injuring 500 others.

Bhutto escaped unhurt as she was in the bulletproof interior of the truck at the time of the blasts.

The home department of Sindh province had issued a warning prior to Bhutto's arrival about fears of suicide bombings at the behest of the Taliban and Al Qaeda.

Officials had also indicated that the longer Bhutto stayed on the road, the more difficult it would be to provide her foolproof security.

Bhutto's convoy was on the road for almost nine hours before the suicide bomber struck.