For the first time in months Hamas escalated its operations and claimed responsibility for Qassam rocket attacks on Israeli cities Tuesday. However, Tuesday's violence was merely the beginning, said senior Hamas figure Mahmoud al-Zahar, whose son was killed in an IDF strike Tuesday. "We shall respond to the crimes committed by the Israelis in the only language which they understand," al-Zahar threatened. Phone interview with Hamas spokesman (Video: Infolive.tv) Al-Zahar added that ongoing IDF strikes in the Strip are a direct result of the go-ahead and backing given by Bush to the "Zionists' continued attacks." The Hamas leader also had a few choice words for the Palestinian Authority, noting that “the current Israeli operation is a direct product of the cooperation between traitors within the Palestinian leadership and the Israeli enemy." “proponents of peace have brought nothing but shame and contempt to the Palestinian people," he said. Officials in the Gaza Strip could not predict whether or not Hamas retaliation against Israel would be especially harsh in light of the death of al-Zahar’s son. Palestinian officials associated with Hamas stated that the organization “doesn’t carry out its operations based on the identity of those killed or injured, but rather, based upon political considerations and conditions on the ground.” Al-Zahar mourns his son. Photo: Courtesy of Reuters This said, Hamas Tuesday claimed responsibility for Qassam rocket fire into Sderot and Ashkelon, this after months of halting attacks on Israel, and striking at IDF outpost surrounding Gaza and Gaza vicinity communities alone. Al-Zahar spend night with Hamas team Although not officially a part of the Hamas-led government, al-Zahar is considered the organization’s most prominent Gaza figure, with marked influence on Hamas’ military wing and on its policies in general. Hamas activists told Ynet that al-Zahar spent a night with the organization’s reconnaissance team, who are charged with keeping track of IDF troop movements in Gaza, after they had lost some members to IDF strikes, in order to bolster the group’s morale. Al-Zahar lost his eldest son, Khalid, to a past IAF air strike on his home, which also left al-Zahar himself lightly wounded. He has championed the movement’s harder political line, unlike Hamas Chief Ismail Haniyeh who has been far more open to negotiating with Palestinian authority president Mahmoud Abbas. Al-Zahar, who is among Hamas’ founding members, is widely held to be responsible for the movement’s coup in the Gaza Strip.