"The Italian diplomats got out of their car in the district of Zawiet al-Dahmani to shop when they noticed a wire hanging beneath the vehicle," a
The driver called the police who blocked the road shortly before the explosion, he said.
"They evacuated the area before the car exploded half an hour later," added the diplomat, who was speaking on condition of anonymity.
That version of events was confirmed by witnesses in the neighbourhood located a few kilometres (miles) from the centre of Tripoli.
The witnesses said the blast was of low intensity and that the car was not completely destroyed.
According to the diplomat, the explosive device was attached to the car in another district of the Libyan capital where the Italians had made a first
In January, the Italian consul in Libya's second city of Benghazi, Guido De Sanctis, escaped an assassination attempt when his armoured car was fired on.
Italy is Libya's former colonial ruler and enjoyed close ties with slain dictator Moamer Kadhafi, although it later joined NATO efforts to unseat him.
Benghazi was the cradle of the 2011 revolt that toppled Kadhafi. The number of attacks against military and police officers, including ones who served the
former regime, has recently spiked in the Mediterranean city.
It has also emerged as a hub for jihadist groups, including militants who killed US ambassador Chris Stevens and three other Americans in an attack on
the US consulate on last year.