Jerusalem (CNN) -- Eleven rockets were fired into Israel from Gaza on Thursday, a day after a fatal terrorist bombing in Jerusalem killed a woman and wounded more than 50 other people, the Israel Defense Forces said.
"The question is why," Brig. Gen. Yossi Kuperwasser said in a phone call Thursday, speaking about the increase in attacks, which the IDF said caused no injuries.
Israel's ambassador to the United States said Thursday the rocket attacks appear "unrelated" to Wednesday's bombing in Jerusalem.
Michael Oren said the rocket attacks probably have to do with infighting in the Hamas-controlled territory of Gaza. However, he said, there has also been an escalation in violence against his country.
"Israel has been under attack on several fronts," Oren said, also citing the recent murder of an Israeli family in the West Bank.
One of the rockets fired Thursday hit near the southern Israeli town of Ashdod, and another landed in the southern town of Sderot, causing damage to an industrial area of the town, according to Israeli Police spokesman Micky Rosenfeld.
In response to the rocket attacks, the Israeli military launched airstrikes in Gaza on Thursday night. Two were in the Beit Hanoun area of northern Gaza and two were in Gaza City, according to journalist Ibrahim Dahman.
A Hamas building and a Hamas training camp were hit, he reported.
Kuperwasser said Thursday night's strikes were aimed at trying to prevent more attacks on Israel.
"Right now there is no one in Gaza to stop this, so it's up to us to try to stop it," he said.
"It seems no one speaks for the Palestinians," he added. "Hamas is not in charge."
There was no immediate claim of responsibility for the Jerusalem attack, which was caused by a medium-sized device in a bag that had been left near Jerusalem's central bus station as the evening rush hour began.
Israel's Ministry of Foreign Affairs named the woman who died as Mary Jane Gardner, a 59-year-old British national who was studying at the Hebrew University in Jerusalem.
Israeli officials were continuing their investigation into Wednesday's attack, Kuperwasser said, without giving details.
U.S. President Barack Obama called Israeli Prime Minister Benjamin Netanyahu on Thursday to express his condolences over the Jerusalem bombing and his concern about the attacks against Israel from Gaza, the White House said in a statement.
Obama "reaffirmed the United States' unwavering commitment to Israel's security," it said.
U.S. Defense Secretary Robert Gates also paid a visit to Israel on Thursday. He met with his Israeli counterpart, Ehud Barak, who said Israel will not "tolerate" terrorist attacks.
British Foreign Secretary William Hague also spoke out against the attack, calling it "a callous and disgusting act of terrorism directed against innocent civilians which I condemn unreservedly."
The Palestinian Authority also condemned the attack, but Oren, the Israeli ambassador, criticized their comments.
They "say one thing" and "do another thing," he said.
He said prominent members of the Palestinian government recently attended a ceremony at a central square near Ramallah that was named after a "Palestinian terrorist who killed dozens of Israelis, including about 13 children."
"The message gets out that killing Israelis is a good thing," Oren said. "We need to see not just words, but deeds."
CNN's Charley Keyes, Michal Zippori, Paul Colsey, and Melissa Gray contributed to this report