Are Iran rocket experts helping militants in Gaza?

Israeli media quotes Palestinian and Israeli sources as saying that Iran's Revolutionary Guard envoys have arrived in the Gaza Strip.

Hamas members take part in a rally 370 (photo credit: REUTERS/Ibraheem Abu Mustafa)
Hamas members take part in a rally 370
(photo credit: REUTERS/Ibraheem Abu Mustafa)
Expert rocket makers dispatched from the Iranian Revolutionary Guards have in recent days arrived in the Gaza Strip, senior Palestinian security sources have told the Israeli news outlet Walla! on Tuesday.
According to the report, the sources said that they are in Gaza to help Hamas and the Islamic Jihad develop long-range missiles. Israeli security and diplomatic sources have reportedly confirmed the Palestinian claims that there is an Iranian presence in Gaza, but did not elaborate. Walla! quoted the Israeli sources as saying that Iranian agents have previously visited the Gaza Strip as well.
On Tuesday morning, a Grad rocket fired from Gaza slammed into a road south of Ashkelon, causing some damage but no injuries.
The Al-Aqsa Martyrs Brigades took responsibility for the attack, Palestinian news agency Ma'an reported. Ma'an said the rocket was fired in response to the "liquidation" of Arafat Jaradat, whose death Saturday in Israeli custody has sparked days of clashes in the West Bank between IDF troops and protesters. 
The Grad was the first missile fired from Gaza since the end of Operation Pillar of Defense in November, a week-long Israeli operation aimed at stemming daily rocket fire from Gaza on its southern communities. For the first time during the operation, Gazan militants fired rockets that reached as far as Tel Aviv.