The Israeli military has carried out air strikes in Gaza, in response to what it claims was a rocket fired towards the country.
At least three Palestinians were wounded in the attack, including one seriously, Ayman Sahbani, an emergency director at Gaza's Shifa hospital.
Palestinian media reports that a 26-year-old man is in serious condition with head wounds from shrapnel.
Israel said the air strikes were targeting two positions of the Palestinian group in response to a rocket fired towards Israel.
On its Twitter account, the Israel Defence Forces said: "A short while ago, a projectile hit an open region in the Ashkelon region. No injuries have been reported.
"In response, IAF aircraft targeted two Hamas posts in the northern Gaza Strip."
But Hamas spokesman Hazem Qasem rejected Israel's claims and told Aljazeera: "The occupation claims that a group from Gaza launched rockets at them, but there is no side in Gaza that claimed responsibility.
"We are maintaining the period of calm and did not launch any rockets. It is not beneficial for the occupation to violate this period of calm."
Since the last conflict between Israel and Hamas-run Gaza in 2014, a ceasefire has largely been held.
Israel has seen occasional rocket fire from the Gaza Strip, with most claimed by Salafist groups in the Palestinian territory.
But Israel holds Hamas responsible for all fire out of the strip including rockets launched by any of the various militant groups challenging it.
Israel and Hamas have fought three wars since the Islamic militant group took control of Gaza, a decade ago.
Last month, Hamas was declared a terrorist organisation by the European Court of Justice (ECJ).
Earlier this year, Hamas published a new manifesto in which it does not explicitly recognise the state of Israel but it accepts the borders of a Palestinian state within the pre-1967 boundaries for the first time.
