Two Iranian-backed Islamic Jihad members among the fatalities as rocket fire towards Israel resumes after brief overnight lull in what is the heaviest round of fighting in months.
The Palestinian death toll from Israeli raids in Gaza has risen to 22, Palestine's health ministry said on Wednesday, as Israel said it carried out further strikes.
"The first martyr, Khaled Farraj, 38, a leading member of Al Quds Brigades, the military wing of the Islamic Jihad group," the ministry said without identifying the second killed.
The situation escalated in Gaza early Tuesday after an Israeli air strike killed Bahaa Abu al Atta, the commander of the Iranian-backed Islamic Jihad group. His wife, Asmaa Abu al Atta, was also killed.
Israeli warplanes also launched air strikes targeting Islamic Jihad member Akram al Ajouri in Damascus, Syria.
Two people, including Ajouri's son, were killed and 10 others injured, but the Islamic Jihad leader remained unhurt.
In retaliation for the Atta killing, the Al Quds Brigades, which is the military wing of Islamic Jihad, launched dozens of rockets towards Israeli cities, to which Israel responded with air strikes across Gaza.
Targeting Iranian proxies
Tuesday's pre-dawn Israeli strike came almost simultaneously as another strike attributed to Israel, which targeted a senior Islamic Jihad commander based in Syria. The strikes appeared to be a new surge in the open warfare between Israel and Iranian proxies in the region.
Iran has forces based in Syria, Israel's northern neighbour, and supports Hezbollah militants in Lebanon. In Gaza, it supplies Islamic Jihad with cash, weapons, and expertise.
Israeli Prime Minister Benjamin Netanyahu has also claimed that Iran is using Iraq and far-off Yemen, where Tehran supports Shia Houthi rebels at war with a Saudi-led coalition backing the government, to plan attacks against Israel. Hamas also receives some support from Iran.
Israel frequently strikes Iranian interests in Syria, but Tuesday's attack in Damascus appeared to be a rare assassination attempt of a Palestinian in the Syrian capital.