"The Embassy of Italy expresses its unreserved condemnation of yesterday's killing of three innocent girls in Furnaj in an aerial bombing by the forces attacking the capital," the embassy said in a statement on Tuesday, Xinhua news agency reported.
The Italian embassy called for immediate end to the armed conflict and all unrestrained aerial bombings, as well as commitment to dialogue, peace democracy and development in Libya.
US Ambassador to Libya Richard Norland said he was "sickened by reports that three young sisters were killed in an aerial bombing conducted in Tripoli by forces laying siege on the capital."
"These tragic and senseless deaths unite us all in calling for an immediate end to the fighting and the start of a political process leading to lasting peace in Libya," the US Embassy tweeted.
Three children were killed and three other civil were injured in an airstrike that hit a house in the Libyan capital Tripoli, according to the Health Ministry's Emergency Service.
The UN-backed government condemned the airstrike, accusing the rival eastern-based army of targeting the civil, which the eastern-based army denied.
Since early April, the UN-backed government has been engaged in deadly armed conflict in and around Tripoli against the eastern-based army, which is trying to take over the country's largest city and overthrow the UN-backed government.
( With inputs from IANS )