It said other targets included "sheds of drones", a rocket manufacturing workshop, naval weaponry, military and training facilities and a munitions manufacturing site.
He also called for council action - "to condemn Hamas for its war crimes against Israelis and Palestinians" and "to pass a resolution designating Hamas as a terrorist organization", just as it did with the Islamic State extremist group and al-Qaida. A large number of projectiles were intercepted by the Iron Dome anti-missile system, while sirens continue to disturb Israeli settlements bordering the Gaza Strip.
Earlier, the Israeli military shelled a Hamas-run checkpoint in the northern Gaza Strip on Monday, killing a Palestinian and injuring one. There were no immediate reports of Palestinian casualties.
They were shot dead by Israeli snipers amid protests which saw thousands of Palestinians mass on the Gaza-Israel border in support of their refugee population.
On Tuesday, Hamas' Qassam Brigades and the Islamic Jihad's Saraya al-Quds claimed joint responsibility for the rockets and mortars fired at Israel, said Mladenov.
Egypt brokered a ceasefire in 2014 that ended a seven-week war between Israel and Palestinian militant factions. The groups said they were striking back after Israel killed more than 100 Palestinians who were protesting along the border. One mortar shell landed near a kindergarten shortly before it opened.
Israeli Prime Minister Benjamin Netanyahu vowed, meanwhile, that Israel would "respond with great force" to the rocket attacks as for more than 24 hours Israeli communities around Gaza lived with the fear having mere seconds to seek shelter from incoming rockets, said Mladenov.
Early Tuesday, some 28 mortar shells were fired toward Israel from the Gaza Strip.
Local attorneys file emergency worldwide request to stop family separations at border
But a recent draconian policy change has cut through the blur to inspire the sustained outrage that it deserves. The ACLU released a report last week alleging that detained immigrant children " suffered pervasive abuse ".
According to the Italian Disarmament Network, in 2014, Italy was the European Union's leading arms exporter to Israel and maintains strong collaboration on military research and intelligence activities. Hamas had urged people to storm Israel's border.
Off Gaza's coast on Tuesday, the Israeli navy intercepted a boat that organisers of the Palestinian border protests launched from the enclave in a challenge to an Israeli maritime blockade.
Both sides continued attacks until before dawn on Wednesday.
There has been wide speculation in Israel and Gaza of a wider peace agreement being discussed between two sides, as tensions have soared in the region over the past few months.
At least 116 Palestinians have been killed by Israeli snipers, tanks and airstrikes since the protests began on March 30.
It was not immediately clear if Islamic Jihad, a much smaller, Iran-backed militant group, acted independently Tuesday or at least had the tacit blessing of Hamas.
The Gaza Strip has been under Israeli blockade for more than a decade, with Israel saying it is necessary to prevent Hamas from obtaining means to attack.