Israeli planes have carried out further air attacks on the Gaza Strip, killing four Palestinian militants.
In the West Bank, Israeli troops killed two people in a raid on Balata refugee camp on the outskirts of Nablus.
In all, 17 Palestinians have died in Israeli military action in the last two days, including a six-month-old baby.
An Israeli student was also killed in escalated Palestinian rocket fire from the Gaza Strip, some of which hit the nearby southern Israeli town of Sderot.
Israeli Prime Minister Ehud Olmert said "terrorists", as he called them, would pay a very heavy price for the attacks.
US Secretary of State Condoleezza Rice said that the Palestinian rocket attacks "need to stop".
"We are all sorry about the death of the Israeli university student," she said after meeting the Israeli prime minister in Tokyo.
She added: "I am concerned about the humanitarian conditions there and innocent people in Gaza who are being hurt."
Ms Rice will visit the Middle East next week for several days of talks with Mr Olmert and Palestinian Authority President Mahmoud Abbas.
UN Secretary General Ban Ki-moon has separately expressed "deep concerned" at the escalation of violence between Israel and the Palestinians.
"These events underscore the urgent need for a calming of violence, and must not be allowed to deter the continuation of the political process," he said in a statement.
A string of Israeli air raids targetted Hamas militants in the Gaza Strip on Thursday morning. In one attack, Hamza al-Haya, son of a prominent hardline leader in the Gaza Strip, Khalil al-Haya, was killed along with a fellow militant.
Palestinian witnesses said the Interior Ministry building, run by the militant group Hamas, was hit on Wednesday evening. The building was empty.
Hamas leaders have been in hiding because of the possibility of Israel assassination attempts.
Nearby buildings were caught in the blast, killing a baby and wounding at about 30 other people, Palestinian medical officials said.
Most of the other recent Palestinian fatalities have been militants, including five Hamas members killed in an air strike in Khan Younis on Wednesday morning.
Hamas Prime Minister Ismail Haniya, whose office was also bombed during the night, condemned what he called "continuous crimes" by Israel.
"The assassinations and the bombardment of civil and governmental buildings are not going to weaken the steadfastness and the determination of the Palestinian people," he said in a statement.
In Balata refugee camp, Israeli troops killed two militants. An Israeli army spokeswoman said troops had opened fire after spotting armed men threatening them.
One of Hamas's rockets exploded in a car park at Sapir College in Sderot late on Wednesday afternoon, killing an Israel civilian who was identified as a 47-year-old father-of-four studying at the college.
Although the Israeli fatality is the first death from Palestinian rocket fire in nine months, four other Israelis have been killed in attacks by Palestinian militants in the last three months, since the relaunching of peace talks between Israel and the Palestinian leadership of Hamas rival Mr Abbas.
In that time, more than 200 Palestinians have been killed by the Israeli army, most of them militants.
An Israeli poll published on Wednesday indicated that nearly two-thirds of Israelis favour direct talks with Hamas to reach a ceasefire and secure the release of an Israeli soldier captured by Hamas in 2006.