Israel advances deep into Gaza urban areas

Troops are moving around
Military analysts say Israeli troops are probing territory, clearing buildings and moving around regularly, rather than digging into positions that would allow Hamas militants to get a fix on their whereabouts and lay ambushes. Israel risks losing the advantage of armor and heavy firepower in urban settings that the militants know well.

Israeli military footage showed soldiers walking around a zoo in the Zeitoun neighborhood of Gaza City two days ago. The footage showed caged birds and a white cable identified as an explosive detonation cord, part of an alleged booby trap set by Hamas.

An Israeli airstrike destroyed a mosque and Islamic school in Rafah, on the border with Egypt. Hours later, men and boys clambered over the wreckage, and one man held aloft the remains of a Quran recovered from the debris.

Israeli has accused Hamas of launching attacks from mosques and schools and using them to hide weapons. Israel says Hamas fighters are wearing civilian clothes and endangering civilians by operating in residential areas.

The Israeli military said it hit more than 40 Hamas militants on Sunday, but did not specify whether they were killed or wounded.

Late Sunday, dense plumes of smoke from explosions rose over Gaza City and heavy gunfire was heard just south of the city.

International aid groups say Israel must do more to ensure the safety of civilians. They note that civilians are in many cases unable to flee to safe places in Gaza, and are essentially trapped because the territory's exits are closed.

U.N. resumes operations
The U.N. agency in charge of Palestinian refugees has resumed operations after suspending them because of Israeli attacks on its convoys. U.N. aid vehicles were moving around Gaza on Sunday and U.N. workers tended to about 30,000 people in shelters, but aid officials warned that the dire security situation made it impossible to operate at full capacity.

"This is a very small fraction of what we normally do in the Gaza Strip," said Filippo Grandi of the U.N. Relief and Works Agency. "Things might get worse."

Israel has warned Gaza residents of a wider offensive. On Sunday, it dropped leaflets urging Gaza residents to report the whereabouts of Hamas fighters, providing a phone number to call.

Israel's chief military spokesman, Brig. Gen. Avi Benayahu, said the army has sent more reserve units into the Gaza Strip.

In other fighting, Hamas militants launched at least 24 rockets at southern Israel, lightly injuring three people. Rockets hit an empty kindergarten and a children's playground in the city of Ashdod.

The rockets have disrupted life for hundreds of thousands of terrified people who rush into bunkers and basements at the sound of warning sirens. Four people have died in rocket attacks.

Students return to school
However, thousands of children in southern Israel returned to school Sunday for the first time in two weeks. Schools had been closed since the beginning of the offensive, but the military said schools that have been sufficiently fortified against attack could reopen.

British Mideast envoy Tony Blair and Germany's top diplomat visited Jerusalem Sunday, and Israel planned to send a senior defense official this week to Egypt, which is trying to broker a truce.

Blair met Olmert and said a plan to end the fighting must include a halt to weapons smuggling and the opening of border crossings into Gaza. He said urgency was vital because "every day this action continues there are more people that die."

Germany's foreign minister, Frank-Walter Steinmeier, appeared at a news conference with his Israeli counterpart, Tzipi Livni, in Jerusalem.

"The shooting of Qassam rockets and other weapons must be stopped and the smuggling of new weapons to the Gaza Strip for re-arming, or even to improve the weapons of Hamas, must be stopped," Steinmeier said.

More on Israel | Hamas | Palestinians

More from msnbc.com Now boarding: Flight 1225 to North Pole Predictions 101: Bowl picks for Christmas weekend Cosmic Log: Pick the year’s weirdest scientific wonders ConsumerMan: Some retailers relax return policies Do you get good abs from sex — or vice versa? Kim Peek, a man who inspired more than ‘Rain Man’ Sluggish new home sales show rocky recovery

MORE FROM MIDEAST & N. AFRICA

Mideast & N. Africa Section Front

Report: Bin Laden daughter hiding in Iran Bombs target Iraqi Christians, Shiites Reports: Iran protesters ‘savagely attacked’ Report: Hasan asked about killing GIs in '08 Destination of N. Korean arms cache is murky Captain of famed Exodus refugee ship dies at 86 Ex-President Carter offers apology to Jews Gates proposes $2 billion for unstable countries Mideast & N. Africa Section Front   Add Mideast & N. Africa headlines to your news reader: