By Nidal al-Mughrabi
GAZA (Reuters) - Israeli air strikes and shelling killed eight Palestinians in the Gaza Strip on Tuesday, medical officials said, in the deadliest day of conflict in the enclave in months.
Palestinian medical officials said three youths aged 12, 16 and 17 who were playing football and an adult relative were killed by Israeli shelling, and four militants were killed later in an air strike elsewhere in the Gaza Strip.
Tuesday's death toll was the highest for a single day in months, provoking calls from militants for revenge, condemnation by a U.N. official and a demand from a Palestinian leader for foreign intervention to stop the violence.
Israeli Prime Minister Benjamin Netanyahu apologized for the civilian casualties and said Israel had no intention of seeking a further escalation of the conflict, but would defend itself against rocket fire aimed at its citizens.
Hamas has stepped up rocket fire aimed at Israel after a hiatus since the two sides fought a war two years ago, and said its fighters had fired more than two dozen mortar shells and rockets at the weekend.
Israel has retaliated with air and ground assaults, saying it was targeting militants firing rockets and mortar shells at its towns and cities.
In Tuesday's raids, Israel killed four militants of the Islamic Jihad group in an air strike east of Gaza City, Hamas officials and medical staff said.
Israel said the militants had been preparing to fire a rocket and the same men had shot a rocket that struck a house in the Israeli city of Beersheba last month.
YOUTHS PLAYING FOOTBALL
Earlier, Israel's armed forces said it aimed mortar fire at militants shooting at Israel. Palestinian medical officials said the Israeli shells struck a house, killing four people and wounding 12, including eight children.
The owner of the house was inside and the youths were outside playing football, witnesses and medical officials said.
Netanyahu issued a statement expressing regret for the "mistaken strike on innocent civilians."
Abu Abdallah Al-Harazeen, an Islamic Jihad leader, threatened in a statement that "blood would beget more blood and by this blood we shall fight Israel again and again."
Hamas spokesman Ismail Rudwan said on the movement's website that "this massacre will not pass easily and the Zionist entity should prepare itself for a tough response."
France's Foreign Ministry appealed to both sides to show restraint, and the U.N. coordinator for Middle East diplomacy, Robert Serry, condemned both sides and called for "an urgent halt to all act of violence."
Palestinian Prime Minister Salam Fayyad urged immediate intervention by the international community to press Israel to curtail its strikes.
Palestinian analysts linked the growing violence to calls for President Mahmoud Abbas to heal a four-year rift with Hamas, which seized control of Gaza in a bloody struggle in 2007 with Abbas's Western-backed Fatah movement.
Some Hamas officials were seen as worried that Fatah could regain control of Gaza if the two groups were reconciled.
(Writing by Allyn Fisher-Ilan; Editing by Douglas Hamilton)