The death toll in Gaza  rose to nine early Monday following overnight Israeli air strikes on the besieged enclave, a Hamas spokesman said.Sami Abu Zuhri told Ma'an that six Hamas fighters  were killed by Israeli air strikes on a tunnel in Rafah overnight. The victims were buried under the debris and only found early Monday.The fighters were identified as Ibrahim Balawi, 24, Abdul-Rahman al-Zamili, 22, Mustafa Abu Mur, 22, his twin brother Khalid, Sharaf Ghannam, 22, and Juma Abu Shalouf, 24.Another militant affiliated with the al-Qassam Brigades succumbed to wounds sustained in an Israeli air strike which targeted a military training base east of Rafah, Hamas said."The enemy's assassination of a number of fighters affiliated to the al-Qassam Brigades  is a dangerous escalation for which the enemy will pay a toll," Abu Zuhri said. A child, two teenage girls and two men were injured by an Israeli airstrike on Beit Hanoun, a Palestinian medical official said.Strikes were also reported  in Khan Younis and Gaza City, with no injuries reported.Earlier, two Palestinian militants were killed by an Israeli air strike on al-Bureij refugee camp in central Gaza.A newly formed military group identified in a statement as Abdul-Qadir al-Husseini Brigades said the two men were members.They were identified as Mazin al-Jidya and Marwan Salim. The An-Nasser Saladin Bridages, the military wing of the Popular Resistance Committee, said its fighters launched two rockets at southern Israel overnight.The Israeli army said it had "targeted nine terror sites and concealed rocket launchers across the Gaza Strip", noting in a statement its attacks came after militants had fired over 25 mortars and rockets at Israel on Sunday.