An explosion was heard in Gaza City on Friday and smoke was seen billowing from the seventh floor of a high-rise building. The Palestinian Health Ministry said 40 people were injured and a senior Islamic Jihad commander and a five-year-old boy were among the dead. The strike comes after days of tension following the arrest of a senior militant in the occupied West Bank on Monday. Israel had closed roads around Gaza earlier this week and sent reinforcements to the border in anticipation of retaliation. “The IDF (Israeli Defense League) is currently striking the Gaza Strip. A special state of emergency has been declared on Israel’s home front,” the Israeli military said in a statement. Palestinian Islamic Jihad (PIJ) and the IDF said the official killed was Tayseer al-Jaabari. According to the IDF he was “responsible for multiple terrorist attacks against Israeli civilians” and shared a photo of him on social media. Hamas spokesman Fawzi Barhoum said that “the Israeli enemy, who started the escalation against Gaza and committed a new crime, must pay the price and bear full responsibility for it.” Image: The Israeli Defense Force shared an image of the targeted PIJ fighter. Photo Twitter/IDF In a statement broadcast by Al Mayadeen TV, a pro-Iranian Lebanese channel, Islamic Jihad leader Ziad Al Nakhala vowed retaliation for the strikes. “There are no red lines in this battle and Tel Aviv will fall under the resistance’s rockets, as will all Israeli cities,” he said. Israeli Defense Minister Benny Gantz visited communities near Gaza earlier Friday, saying authorities were preparing “actions to remove the threat from this area,” without elaborating. Image: Palestinians react at a hospital after Israeli strikes in Gaza City Read more from Sky News: ‘Every civilian casualty is tragic’ Crisis management not peace talks “We will operate with internal resilience and external strength in order to restore routine life in southern Israel,” he said. “We do not seek conflict, however we will not hesitate to defend our citizens if necessary.” The PIJ is smaller than Hamas but has a similar ideology, with both groups opposing Israel’s presence.