(adds details, factions meet on fate of ceasefire)

GAZA, Dec 2 (Reuters) - An Israeli air strike killed two Palestinian youths on Tuesday in the southern Gaza Strip, where mortar bombs were earlier launched at Israel, local residents and hospital officials said.

The Israeli military confirmed an air strike had taken place on the town of Rafah, in which two other people were wounded. It said militants had fired six mortar bombs across the border.

Rafah residents and hospital officials said the two Palestinians killed were civilians who were related. One was aged 15 and the second was 17.

The Hamas Islamist faction that controls the Gaza Strip said one of its members was wounded in the strike.

Militants have fired dozens of rockets and mortar bombs at Israel in the past three weeks after Israeli raids that killed about a dozen gunmen. The violence has strained a ceasefire which was agreed last June.

Saying it was responding to rocket attacks, Israel has tightened its closure of Gaza's border crossings, stopping supplies into the territory and raising international concern.

Later on Tuesday, leaders of Hamas and the less influential Islamic Jihad militant group met to discuss the fate of the six-month-old ceasefire and blamed Israel for weakening the chances it could be renewed.

The six-month ceasefire was set on June 19 and is due to expire later this month.

"If we ask our Palestinian people today we would not find many in favour of continuing the calm agreement the way it is now," senior Hamas leader Khalil al-Hayya said before entering the meeting.

Hayya said Israel had also not abided by the agreement when it did not fully open the crossings it controls with Gaza to allow the transfer of goods and it had not stopped military strikes in the occupied West Bank and in the coastal territory.

Senior Islamic Jihad official Nafez Azzam said Tuesday's killing of the two teenagers in Rafah was a "proof the aggression was continuing".

The officials said their decision on the future of the truce would be relayed to Egyptian mediators. (Reporting by Nidal al-Mughrabi, Writing by Dan Williams; editing by Ori Lewis)

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