BEIRUT, June 23 (Reuters/Yara Bayoumy) - The head of the United Nations' Palestinian refugee agency said on Wednesday the fine print of Israel's pledge to ease its Gaza blockade raised questions about how effective it would prove to be.

Under international pressure over an Israeli commando raid on a relief aid flotilla bound for Gaza that killed nine people, Israel last week announced it would relax its grip on Gaza.

Israel imposed the blockade in 2007 to try to weaken the Islamist Hamas, which refuses to recognise Israel and which seized control of the Gaza Strip that year, and prevent it from acquiring more and heavier weapons.

Israel's rules banned any import into Gaza that was not explicitly permitted. Israel now says it will let in all goods except those on a list that could be used for military purposes, including cement and steel rods.

Filippo Grandi, commissioner-general of the refugee agency known as UNRWA, called the blockade absurd, counterproductive and illegal and cited elements in Israel's easing plan that left unclear how it would be fully implemented.

They're talking about items that will be allowed for certain times and not other times, depending on who the consignee is. So it's still very complicated, he told reporters in Beirut. We have seen some broad statements of how they will do it but the devil is in the detail. We have to see how this will be done and we haven't seen it yet.

We've seen many times declarations and statements, Grandi added. But now we want to see facts ... Believe me, it's very urgent, because the conditions are very bad on the ground.

Human rights groups and other critics see the blockade as collective punishment of Gaza's 1.5 million Palestinians.

Israel denies there is a humanitarian crisis in Gaza, as Palestinians, UNRWA officials and rights advocates maintain.

Critics have said Israel's new rules could still make it hard to import building materials to rebuild the coastal enclave, whose tattered infrastructure suffered severe damage in a war between Israel and Hamas in early 2009.

Grandi called for Gaza's land crossings to be opened.

UNRWA has said Israel must reopen the Karni cargo terminal on Gaza's northeast boundary that is large enough to allow industrial-scale shipments of cement, building materials and aid. Instead, trucks are now routed to a narrower crossing.