GAZA CITY (CNN) -- Rockets landed near Israel's two most populous cities Friday as fighting between Israel and Hamas militants persisted with no immediate end in sight.
Two rockets hit in an open area south of the city of Jerusalem, and no damage was reported. Hamas militants confirmed that they had fired rockets toward the city, which Israel considers its capital but is not recognized as such by the international community.
Air raid sirens also sounded in Tel Aviv, but officials said rockets fired toward that city did not hit land, but might have landed in the sea.
The fighting has left 28 dead and at least 270 wounded since Wednesday, including a high-level Hamas military commander who was killed Friday, according to Gaza medical sources. Three Israelis have been killed in the same period.
The injured include 101 children and 96 women, said Dr. Mufeed Mkhallalati, the Palestinian health minister.
Hamas field commander Ahmad Abu Galala was the military leader killed Friday, Hamas officials said.
The Israelis consider the firing of rockets at its major population centers to be an escalation, said Israel's ambassador to the United States, Michael Oren.
Oren defended the Israeli airstrikes, saying that more than 2,500 rockets had been fired at Israeli since its last incursion into Gaza in 2009.
On Friday, 97 rockets launched from Gaza hit Israel, and another 99 rockets were intercepted by Israel's missile defense system, the Israel Defense Forces said.
The Israeli government could not continue to show "superhuman restraint" in response to the attacks, Oren said.
"We hope it doesn't become war," he said. "Right now it's an armed conflict."
The IDF accused Hamas of turning Gaza into "a frontal base for Iran."
Gazans got no respite from the ongoing attacks as Egypt's prime minister arrived for a visit. Israel planned a cease-fire for Friday to accommodate him, according to a senior official from the Israeli prime minister's office. But the move was contingent on Gazans also holding their fire.
The militant group al-Qassam, Hamas' military arm, rejected the idea. In fact, al-Qassam reported on its Twitter feed that it had fired a Grad missile on the southern Israeli city of Beer Sheva.
The military began operation Pillar of Defense on Wednesday in response to the high number of rockets fired at Israel over the past year.
The Israel Defense Forces reports it is "mobilizing forces" in preparation for "a possible ground invasion of the Gaza Strip." Israel's Cabinet on Friday approved the activation of up to 75,000 reservists given the conflict, said prime minister's spokesman Mark Regev, a figure that's more than twice the 30,000 troops the military said earlier Friday were being mobilized to potentially go into Gaza.
Western powers largely blame Hamas for starting the armed altercation, but they have urged Israel to be proportionate in its response.
In Gaza City, recurring bombardments provided for a sleepless night of hearing and feeling explosions of ordnance coming into Gaza from Israel and watching some rockets leaving Gaza for Israel.
Clouds of smoke sprouted into the sky, paralleling the thunderous booms from bombs that made doors clatter, if they didn't tear them apart.
The bomb clouds in Gaza could be seen from Ashkelon, Israel, in the morning light, and the loud rumble of their explosions could be heard.
Palestinian Authority president condemns strikes
Through its attacks, Israel is denying Palestinians their rights and efforts to establish an independent state, Palestinian Authority President Mahmoud Abbas said Friday.
"This is an aggression against all Palestinian people," he said.
He cited the deaths of two babies as a result of Israeli airstrikes. One of the babies was the 11-month-old son of a BBC journalist in Gaza, BBC Foreign Editor Jon Williams said.
Oren said any loss of life is regrettable, but the Israeli military takes great pains to avoid civilian casualties.
The Arab League will hold a meeting to address the conflict on Saturday.
Israeli authorities said the military campaign has hit relevant military targets and stifled the launching of rockets out of Gaza.
According to Hamas, the Israeli air force struck its Interior Ministry, a claim backed up by press photos of fiery rubble where the building once stood and comments retweeted by Israeli spokeswoman Avital Leibovich.
Gazan militants from al-Qassam denied Israeli reports that their attacks had lightened up. They claimed to have hit multiple Israeli targets Friday with Grad and Qassam rockets. Qassam announced it had directed a rocket at the Knesset, Israel's parliament, but Leibovich said no rocket had hit there.
High-level visit from Cairo
As Kandil, the Egyptian prime minister, got a firsthand look at fresh destruction and casualties on a tour with Hamas Prime Minister Ismail Haniyeh, fears of a ground invasion by Israel seemed to gain support.
Kandil openly showed emotion over the death of a year-old boy. He read a verse out of the Quran in respect to the fallen Palestinians.
His rhetoric toward Israel was diplomatic, though his voice was halting, and he struggled at times to get his words out.
"No one can remain still and watch this tragedy unfold in this fashion," Kandil said. "This is impossible. The whole world must intervene, and Israel must abide by the agreements and stop the aggression."
The armed conflict is likely to further erode Israel's fragile relationship with Egypt, which recalled its ambassador to Israel on Wednesday in protest over the ongoing strikes. It also delivered a formal protest to the Israeli government.
"Egypt will not leave Gaza alone and what is happening there is a blatant aggression against humanity," said Egyptian President Mohammed Morsy.
His Cabinet chief, however, said Egypt's peace treaty with Israel is safe.
"But respecting a peace treaty does not mean to stay idle or indifferent to what is going on along our borders," Mohamed Refa'a al-Tahtawi said.
In a Friday evening interview with CNN, al-Tahtawi promised practical support from Egypt in the form of "medical, logistical and humanitarian measures ... will be taken."
Since the start of Operation Pillar of Defense, the Israeli Air Force has targeted more than 600 sites in Gaza for what it calls terror activity. In addition to airstrikes, the Israeli navy has taken aim at targets along Gaza's shoreline, the IDF said.
Israel said it has called thousands of residents in Gaza to warn them of strikes and dropped leaflets in Gaza warning Palestinian civilians to "avoid being present in the vicinity of Hamas operatives," the IDF said.
It also said it uses "roof knocking" -- targeting a building "with a loud but nonlethal bomb that warns civilians they are in the vicinity of a weapons cache or other target. This method is used to allow all residents to leave the area before the IDF targets the site with live ammunition."
Q&A: Gaza strikes could be beginning of ground attack
Western officials express concern
The European Union's High Representative Catherine Ashton expressed concern Friday over the mobilization of IDF troops. She urged Israel to be "proportionate" in its response but blamed Gazan militant groups for starting the violent exchange.
"Israel has the right to protect its population from these kinds of attacks," she said.
U.S. Defense Secretary Leon Panetta, speaking Friday during a visit to Bangkok, Thailand, said he believes Israel and the Palestinians need to negotiate "a more permanent peace in that region."
"I understand the reasons Israel is doing what they're doing," he said.
U.N. Secretary-General Ban Ki-moon will go to Egypt and Israel next week because of the rising tensions between Israel and Hamas, a Western diplomat told CNN.