Three of the Palestinians were killed while preparing to launch rockets from Gaza, Ynetnews.com reported.
The others were killed several hours later as they attempted to plant a bomb at a security fence along the Gaza-Israel border.
Palestinians said shelling from one of the attacks in Beit Hanoun seriously injured three civilians near an agricultural college.
Palestinian health official Ashraf al Kidra said Israeli forces prevented medical teams from reaching the injured.
Reports differed on how the attacks were conducted. Ynetnews said the men were killed by military aircraft. The Palestinian Wafa news agency said tanks fired on the men.
In the second attack, late Wednesday night east of the al Brij refugee camp in central Gaza, one person was seriously hurt and taken to a hospital for treatment, Wafa reported.
Palestinian spokesman Nabil Abu Rudeineh condemned the attacks, saying they created a destructive atmosphere. He called on the international community to help bring a halt to the Israeli attacks.