The death toll varied as reports emerged from Gaza. At least 11 of the Palestinians killed in Israeli assaults were civilians, Hamas and medical officials told Reuters. At least three youths, a 67-year-old man, a Reuters cameraman and four Hamas gunmen were among the Palestinian dead.
The attacks followed the killing of three Israeli troops in a Hamas ambush near a border fuel pipeline.
Israeli defense officials told the Associated Press that the soldiers had entered Gaza in pursuit of two Hamas militants who planted a bomb near the border. The soldiers were then ambushed by another Hamas force lying in wait, the officials said.
Despite being the bloodiest day in more than a month, Israel allowed European-funded fuel to continue flowing into Gaza to keep its only power plant running. The Nahal Oz fuel terminal was shut down by Israel on April 9 after militants killed two Israeli civilians at the facility.
The bloodshed marked a sudden spike in violence in the Gaza Strip, which had experienced a relative lull since Israel ended a broad offensive in the area in early March. The Israeli army, however, often runs operations into Gaza to prevent Palestinian militants from firing rockets into southern Israel.
In Wednesday's deadliest incident, an Israeli helicopter fired four missiles at targets near the Bureij refugee camp in central Gaza, the AP reported. At least eight Palestinians, including two youths, were killed, Dr. Moaiya Hassanain of the Palestinian Health Ministry said.
In a separate attack, Reuters cameraman Fadel Shana, 23, who survived a 2006 Israeli airstrike on his vehicle, was killed after he stepped from his vehicle, apparently to film Israeli forces positioned several hundred yards away. At least two bystanders were also killed in an explosion.
Shana's soundman, Wafa Abu Mizyed, also in his 20s, sustained a shrapnel wound and was being treated in a Gaza hospital, but he had no immediate recollection of the incident.
Four journalists have been killed covering the West Bank and Gaza Strip since 1992, according to the Committee to Protect Journalists.
In a separate development likely to stoke anger in Israel, Hamas said former U.S. President Jimmy Carter, who planned to travel later in the day to Egypt, would meet in Cairo with two of its Gaza-based leaders, Mahmoud al-Zahar and Saeed Seyam.
"Mr. Carter asked for the meeting. He wanted to hear the Hamas vision regarding the situation, and we are interested in clarifying our position and emphasizing the rights of our people," Hamas official Ayman Taha said.
Carter's delegation in Israel declined to comment.
Zahar, speaking in Gaza before leaving for Egypt, said Carter had been able "to break all the restrictions preventing him from meeting Hamas leaders."
Israeli leaders have shunned Carter over his contacts with Hamas, which has rejected Western demands to recognize Israel, renounce violence and accept existing Israeli-Palestinian interim peace deals.