A Lebanese army officer was wounded Tuesday when an Israeli cluster bomb exploded as he was trying to defuse it in south Lebanon, the official National News Agency reported. Chief Sergeant Khaled al-Ak, 35, was hospitalized after being moderately injured on the outskirts of the southern village of Ansar near the market town of Nabatiyeh. At least 28 people have been killed by cluster bombs and land mine explosions in Lebanon since the 34-day war between Israel and Hezbollah guerrillas ended in a UN-brokered cease-fire on Aug. 14. The United Nations and human rights groups charge Israel dropped about 4 million cluster bomblets during the war. UN ordinance clearing experts say that up to 1 million failed to explode.