Hamas militants who recently returned to the Gaza Strip after training in Iran have a detailed plan for upgrading the capabilities of the rockets being developed in the Strip, according to senior Palestinian Authority sources.

A senior Palestinian source told Haaretz this week that members of Hamas' military wing smuggled blueprints and other detailed technical instructions into the Strip that will enable the group to develop rockets capable of striking at longer distances.

The PA source was unable to estimate the actual distance that these upgrades will allow the Qassam rockets to cover, but said that the aim is to strike at communities north of Ashkelon, which is approximately 15 kilometers north of the northern border of the Strip.

Israeli security sources said recently that Islamic Jihad militants in the Gaza Strip have developed their own upgraded version of the Qassam rocket, with an estimated range of 18 kilometers.

Iran is investing significant efforts in trying to increase the striking distance of the rockets manufactured by Palestinians in Gaza. The militants there have only a limited supply of Grad-type Katyusha rockets, capable of striking targets 20 kilometers away.

And the stockpiles of Katyusha rockets in Gaza, according to the PA source, have dwindled since the fighting three weeks ago, although Iran has smuggled more Katyushas, made by its own military industries, into the Strip by sea, and has also stepped up its efforts to develop more effective rockets locally in the Strip.

The senior Palestinian source said that the technical information for improving the rockets was smuggled into the Strip following January's breach in the Philadelphi Route wall, which separates the Gaza Strip from Sinai and Egypt.

The source added that some 200 Hamas militants who received training in Iran, the Beqa'a Valley in Lebanon, and Syria, returned to the Strip through this breach in the wall.

Hamas and Hezbollah militants are being trained in Iran together, and are learning the same fighting doctrines.

In addition to the experts in rocket development, militants with specialized training in guerrila warfare also snuck back into the Strip. These men received specialized training in the use of anti-tank missiles, laying road-side bombs, and tactics for carrying out defensive operations against a possible IDF invasion of the Strip.

The PA sources said that it is possible that among those who returned after the breach in the wall to the Strip are members of PFLP-GC.