GAZA CITY (Ma'an) -- Two militant groups in Gaza on Tuesday said they fired rockets across the border in response to a barrage of Israeli attacks on the Gaza Strip.
An Israeli military spokeswoman said 16 rockets were fired at southern Israel on Tuesday, causing no injuries.
The Abu Ali Mustafa Brigades, the armed wing of the Popular Front for the Liberation of Palestine, said it fired two mortar shells at Israel's Kissufim military base shortly before 4 p.m.
The brigades will continue to use all methods of resistance against anyone that targets the Palestinian people, the group said in a statement.
PRC's military wing the Nasser Salah ad-Din Brigades said it fired three projectiles into southern Israel in response to Israeli attacks which have killed six Palestinians since Monday.
"The enemy knows well that the resistance acts without warning, and stands beside our people and defends them," the brigades said in a statement.
"The enemy won't impose the regulations of the game this time on the resistance. If the enemy does not stop its crimes, the resistance will respond with all available defense means," the group added.
Hamas' armed wing, the Al-Qassam Brigades, on Tuesday fired its first cross-border rockets in more than a year as fighting along the Israel-Gaza frontier flared for a second day.
For months, Hamas has stayed on the sidelines and discouraged smaller militant groups from firing rockets into Israel.
Fawzi Barhoum, a Hamas spokesman, said Israel's barrage of attacks prompted the group's military wing "to take a firm stance" and launch rockets.
Although Hamas usually holds its fire under an unofficial truce, Israel says it holds the ruling party responsible for any attacks from the Gaza Strip.Reuters contributed to this report.