Gaza toll nears 100, Israel to counter rockets 'with all power'
* Militants warn they will fire rockets at Israel's main airport
* Netanyahu does not rule out ground invasion into Gaza
* 97 Palestinians, many civilians, killed in Israeli strikes
* Gaza militants fire rocket salvoes deep into Israel
Rockets fired from Lebanon have struck Israel as long-range missile fire from Gaza continued against the country for a fourth day.
Israeli military spokesman Lt Col Peter Lerner said the rocket fire struck near Israel's northern border.
He said the military responded with artillery fire toward the apparent source in southern Lebanon. There were no reports of injuries.
Lebanese security officials said militants fired four rockets around 6am local time, and the Israelis retaliated by firing about a dozen artillery shells on the area.
Lebanese troops and United Nations peacekeepers later began searching the area.
That area in southern Lebanon is a stronghold of the Shia militant group Hezbollah, which has battled Israel numerous times. However, past fire from Lebanon has been blamed on radical Palestinian factions in the area and Hezbollah has not been involved in the ongoing offensive.
Lt Col Lerner said Israel has suspected that Lebanese militants may try to join the fray as Israel exchange fire with Islamic Hamas militants in Gaza.
However, he said it is still unclear whether the most recent attack is "symbolic or something more substantial."
Gaza militants already have fired more than 550 rockets against Israel in the four-day offensive. Israel's "Iron Dome" defence system has intercepted most of those aimed at major cities but some have slipped through.
On Friday, one such rocket struck a petrol station in the southern city of Ashdod, setting off a large blaze and sending plumes of smoke into the air. Israeli media reported one person was seriously wounded in the blast.
Air raid sirens sounded once more across the country today, including for the first time in the northern city of Haifa.
In Gaza, an Israeli airstrike hit the home of a known Islamic Jihad leader.
Gaza health officials said five people were killed in the strike, raising the death toll there to at least 90, including dozens of civilians.
Lt Col Lerner said the military was doing its utmost to prevent civilian casualties, calling inhabitants ahead of time to warn of an imminent attack. He said Israeli forces also fire "non-explosive munitions" at roofs as a warning and looks for people to leave before destroying a structure.
Israel launched the Gaza offensive to stop incessant rocket fire. The military said it has hit more than 1,100 targets already, mostly what it identified as rocket-launching sites.
He said it was Hamas itself that was responsible for the death of innocent bystanders by firing from heavily populated areas.
Israel's military "uses its weapons to defend its civilians. Hamas uses its civilians to defend its weapons," he said.
Earlier, Barack Obama had offered the help of the United States in negotiating a ceasefire to end escalating violence between Israel and Hamas.
The US president's intervention came as world leaders warned of an urgent need to avoid another Israeli-Palestinian war that could engulf the fragile region.
In a phone call with Israeli prime minister Benjamin Netanyahu, Mr Obama supported Israel's efforts to defend itself against rocket fire from the Hamas-controlled Gaza Strip, but also called on both Israel and the Palestinians to protect civilians and restore calm.
The White House said the US was willing to "facilitate a cessation of hostilities," potentially along the lines of a 2012 ceasefire that the US helped broker.
Mounting casualties and the growing prospect of an Israeli ground incursion in Gaza drew alarm at the United Nations.
Secretary-General Ban Ki-moon told an emergency Security Council meeting that it is more urgent than ever to avoid another Israeli-Palestinian war that could engulf the entire region. He called on both sides to agree to a ceasefire.
"It is unacceptable for citizens on both sides to permanently live in fear of the next aerial attack," he said.
More than 85 people have been killed, including dozens of civilians, since Israel began an offensive on Tuesday against the Hamas militant group in Gaza.
The offensive aims to put an end to unrelenting rocket fire from Gaza that has reached ever deeper into the Jewish state and intensified amid spiralling tensions over the killing of three Israeli teenagers and the apparent revenge killing of a Palestinian teenager.
The offer to help bring about a ceasefire could draw the US deeper into a conflict the US fears could destabilise the region, but precisely what role the US would play remains unclear.
The United States considers Hamas to be a terrorist organisation and has a policy barring contact with its leaders.
A senior Obama administration official said the policy has not changed but that other players in the Middle East could act as intermediaries, as was the case when Egypt and former Secretary of State Hillary Clinton worked to secure the November 2012 ceasefire. Egypt, Turkey or Qatar are all possibilities, said the official.
In the phone call, Mr Obama condemned the rockets and said Israel has the right to self-defence, the White House said.
Pro-Israel politicians in the US and the State Department have insisted that Hamas is to blame for the fresh round of conflict.
Mr Obama also raised his concerns about Tariq Abu Khdeir, a Palestinian-American teenager who was detained and apparently beaten by Israeli authorities.
The White House said: "The president expressed concern about the risk of further escalation and emphasised the need for all sides to do everything they can to protect the lives of civilians and restore calm. But he also urged both sides not to escalate the crisis."
In a moment of drama at the UN, Israel's ambassador suddenly played the piercing 15-second siren that warns Israelis to run to bomb shelters to escape rocket attacks to highlight the threat his country faces.
Ron Prosor told the council that Hamas is "intentionally and indiscriminately" threatening 3.5 million Israelis and "no nation, no people and no government could tolerate this."
Palestinian UN envoy Riyad Mansour had no props for his appeal to the council "to stop the bleeding" and revive the Palestinians' "dying hopes" for an end to the conflict and peace with freedom.
"I speak on behalf of the suffering and grieving Palestinian people, who are enduring yet another barrage of death, destruction, trauma and terror," he said.
Diplomats said Jordan has circulated a press statement, which is not legally binding, for the Security Council's consideration that would call for a ceasefire.
The draft calls for "immediate calm and ending the hostilities in Gaza including the launching of rocket attacks," restoration of the 2012 ceasefire and resumption of direct Israeli-Palestinian negotiations aimed at a comprehensive peace agreement and a two-state solution. It also calls for protection of civilians.