The recent rockets were "being fired at the wrong time" and were "not being fired by the resistance faction", a statement from the interior ministry of the Hamas government said on Thursday.
It added that its security forces would find out who was responsible, but stopped short of promising any punitive measures.
The rare criticism of the rocket fire - the first since Israel halted its three-week war on Gaza on January 18 - comes as the Palestinian Centre for Human Rights raised the toll from war from 1,300 to 1,434 Palestinians killed.
Of that number, 960 were civilians, the centre said, up from the previous 900 figure.
The Hamas-run health ministry in Gaza puts the toll at 1,324, but Israel says civilian casualty figures have been inflated, claiming it has the names of more than 700 Hamas fighters killed in the fighting.
Israel holds Hamas responsible for all weapons fired at Israel from within Gaza, not accepting that any faction may be taking armed action without Hamas's approval or tolerance.
It said it launched the offensive against Gaza, in which 13 Israelis were killed, to stop the rocket fire. A Palestinian human rights group says the Gaza toll has risen to 1,434.
But rocket fire - 176 launched according to the Israeli military - has continued, though none of it has been fatal in the weeks since Israel and Palestinian factions separately declared ceasefires.
Israeli air assaults have also not ceased, with planes bombing Gaza targets almost daily, though with far fewer casualties than during the three-week all out offensive.
The two sides, along with mediators such as Egypt, have not been able to cement a more lasting ceasefire.
Hamas wants Israel to lift its crippling blockade of border crossings into Gaza which the 1.5 million Palestinians in the territory rely on for the supply of vital goods and services.
Israel says it allows essential food and medicine into Gaza, but will not lift restrictions on the crossings until rocket fire stops completely and an Israel soldier captured in 2006 is released.
The Israeli question, which has long caused difficulty among warring Palestinian factions, continued to plague the groups as they tried to hammer out a power-sharing deal in Egypt on Thursday.
Fawzi Barhoum, a Hamas spokesman, said disagreement over peace talks with Israel was one of the key hurdles holding up the formation of a new unity government between Hamas and the Fatah faction led by Mahmoud Abbas, the Palestinian president.
Egypt, which is mediating between rival Palestinian factions in the talks that began this week in Cairo, and Fatah have repeatedly said that any new Palestinian government should accept previous peace agreements with Israel and the Arab world's peace overtures to the Jewish state.
But Barhoum told The Associated Press in Cairo that Hamas was "not part of these agreements, and therefore, no one should expect us to endorse them".
Instead, Hamas wants the concept of the Palestinians' right to resistance against Israeli occupation be included in the political agenda of any future unity government, said Ibrahim Aboul Maja, a Fatah official.
Despite a move on Thursday by Abbas to release 45 Hamas members being held in the West Bank, Azzam al-Ahmed, another Fatah leader, said the factions had made little headway towards Egypt's stated aim of getting some sort of agreement by Saturday.