The August 7, 1998, bomb attack on the US Embassy in Kenya killed 213 people and injured more than 5,000 others.
A twin blast masterminded by the Osama bin Laden-led Al Qaeda terror group killed 11 people at the US Embassy in Dar es Salaam and injured 85 others.
Twelve Americans died in the attacks, including two CIA agents at the Nairobi embassy.
The death toll in Dar es Salaam was low because the embassy was located outside the city centre. A water truck also prevented the suicide car from getting closer to the building.
Kenya was overwhelmed because it had never witnessed a terror attack of such magnitude.
During the 20th anniversary of the deadly bombing on Tuesday, in a tweet, the US government paid tribute to Kenyans who died or were injured in the attack.
It also paid tribute to the Kenyans who responded with rare acts of heroism and rescued the injured or helped retrieve bodies from the debris.
“Today, we remember and honour all who died or were injured. We remember, too, their family, friends and colleagues. To everyone who suffered that day: you are in our hearts, minds, and prayers,” it said.
It added: “As we remember the sadness of that day, we recall also the acts of heroism, compassion, and caring. So many people assisted the injured, comforted the victims or retrieved the bodies of those who had died.”
Records by the FBI show the attack was masterminded by Osama bin Laden assisted by the current Al Qaeda leader Ayman al-Zawahiri.
Fazul Mohammed, who was later killed by Somali forces in 2011 in Mogadishu, executed the plan in the Kenyan attack, while Abdullah Ahmed commanded the twin attack in Tanzania.
The bombings were widely believed to be revenge for US involvement in the torture of members of the Egyptian Islamic Jihad.
Egyptian Islamic Jihad is a terrorist group whose original mission was to overthrow the Egyptian government and replace it with an Islamic state.
It, however, later widened its ambition to include attacking American and Israeli interests inside and outside Egypt.
Between June and July 1998, the US assisted in the extradition of four of its members who had been arrested in Albania for alleged involvement in murders in Egypt.
The four were also accused of assassinating an Egyptian politician and speaker of the country's Parliament and plotting attacks on Khan el-Khalili market in Cairo.
Initially, Bin Laden attributed the attacks on retaliation for the US invasion of Somalia and an alleged plot to partition Sudan.
He said the plot was hatched at the Nairobi embassy.
Plans for Nairobi embassy bombing began in May. A house was purchased where the bombers assembled a bomb.
US fugitive Sheikh Ahmed Salim Swedan bought a Toyota Dyna, in which the bomb was built. He also bought a refrigeration truck which was used in the Dar es Salaam bombings.
Bomb-making for the Dar es Salaam attack began in June 1998. Mohammed Odeh supervised the making of both bombs.
The Nairobi bomb was made of 400 to 500 cylinders of TNT ammonium nitrate, aluminium powder and a detonating cord.
The explosives were packed into 20 specially designed wooden crates that were sealed and placed in the truck used for the bombing.
The Dar es Salaam bomb had the TNT connected to oxygen cylinders which were surrounded by four bags of ammonium nitrate fertiliser and sandbags.
Available records show the August 7 date was chosen by Bin Laden to coincide with the eighth anniversary of the arrival of U.S. troops in Saudi Arabia during the early stages of the Persian Gulf War.
Between 10:30 a.m. and 10:40 a.m, suicide bombers drove the explosive-laden trucks to the embassies in Nairobi and Dar es Salaam. The bombs were detonated almost simultaneously.
The suicide bomber in Nairobi drove the truck between the Ufundi Cooperative House and the US embassy.
His two assistants fired warning shots at guards after they hesitated to open the gate, while another one hurled a hand grenade.
Most of the 213 Kenyan victims were killed at Ufundi House which collapsed when the 900kg bomb exploded.
Heat from the blast spread across Haile Selassie Avenue and burnt a commuter bus.
Most of the people who sustained eye injuries in nearby buildings had rushed to their office windows to check what was happening. The hand grenade went off first, then the main explosion occurred, shattering windows.
Windows in buildings that were within an 800m radius from the blast scene were shattered.