Israel has partially reopened the main goods crossing into the Gaza Strip after closing it for more than two weeks because of "security alerts".
The Karni crossing has been closed for 40 days during 2006
The closure of the Karni crossing meant basic food commodities, including wheat flour, were no longer available, a UN report published on Wednesday said.
The crossing had been closed since 21 February and has not been open for more than 12 days since the start of 2006.
Palestinian officials said the closures amounted to collective punishment.
The Israeli army first closed the Karni crossing between 15 January and 5 February.
It was closed again last month because the army believed Palestinian militants were planning an imminent attack on the terminal.
A US-brokered deal last November specified that Karni would be kept open unless there was an immediate security threat.
"The decision to open the crossing was made despite existing security alerts and after both humanitarian and security aspects were all taken into consideration," an Israeli statement said.
The Palestinian official in charge of the border, Salim Abu Safiyeh, confirmed Karni had re-opened, but only for food and medicine.
Trucks would not be allowed to leave Gaza for Israel until Sunday, he told Reuters.
"It is a step in the right direction, but it is not enough," he said.
"We need the crossing to open as normal and to be in full operation."
The report by the UN Office for the Coordination of Humanitarian Affairs found that Karni had been closed so far for 40 days in 2006 - 60% of the time.
The crossing was closed for 18% of 2005 and 19% in 2004.
The closures meant there have been severe shortages of wheat flour, dairy products, especially milk, fruit and construction materials.
Palestinian agricultural exports have also been halted, forcing farmers to dump tonnes of spoiled produce.
On 6 March, 50 tonnes of tomatoes and 5 tonnes of peppers were dumped in a landfill in Netzar Khazani.
The Palestinian Trade Centre (PalTrade) estimates the most recent closure caused losses of $7 million.
The total economic losses so far in 2006 are estimated at more than $17 million.
The Palestinian Authority rejected an Israeli offer to use the smaller Kerem Shalom crossing in southern Gaza while Karni remained closed on the grounds that it might turn into a permanent arrangement.
The UNOCHA was also sceptical of the Israeli army's reason for the closure - that Palestinian militants were digging tunnels leading to the crossing.
"At the request of the IDF [Israel Defence Forces], Palestinian security services have dug four trenches, totalling more than one kilometre in length around the crossing, in an effort to find these tunnels. So far, none have been found," it said.
In other developments, the Israeli military said it arrested 13 suspected militants in overnight raids across the West Bank.
Six people were arrested near the town of Tulkarm, including three brothers, who had their house destroyed.
In Nablus, four Palestinians were arrested in the Askar and Balata refugee camps.
Three others were arrested in Bethlehem.