By Nidal al-Mughrabi GAZA (Reuters) - An Israeli air strike killed three militants in the Gaza Strip on Friday, the Islamist group Hamas said, after an overnight clash killed a fourth Palestinian gunman and wounded five Israeli soldiers. The Israeli military said its aircraft targeted a tunnel used by militants to facilitate attacks on Israelis and accused Hamas, Gaza's rulers, of breaching the terms of the ceasefire. A Hamas source said three of its men were in the tunnel at the time of the attack and were killed in the blast. Hours earlier, one Palestinian militant was killed and five Israeli soldiers wounded after violence broke out when Israeli forces detonated part of a separate tunnel that they had recently uncovered stretching from Gaza into Israel.