— The first to fall to Israel’s ground offensive in the Gaza Strip were the shepherds and farmers of the Bedouin village of Um Al Nasser, who say they saw Israeli soldiers come out of the smoke to order everyone in schoolboy Arabic, “Go south!”

For hours, the residents of Um Al Nasser said they were subjected to the opening salvos of Israel’s overnight ground incursion, first with naval barrage, then artillery, flares, smoke bombs, and finally tanks and troops.

“We now have Israelis in our houses,” said Talal Abu Hashish, a farmer, who fled the town in the morning, one of the last to leave.

The empty village sits, surrounded by a sewage lagoon, just 600 meters from a high gray wall that separates this section of the Gaza Strip from Israel. An Israeli observation tower looms above, and the wall bristles with “smart fence” technology — infrared cameras, ground radar, motion detectors and remote-controlled machine guns that swivel and aim with a touch of a toggle switch miles away. The people of Um Al Nasser knew they are under constant surveillance. Gazans who approach too close to the wall have been shot.

Raed Mismeh, a college student from the town, said the invading Israeli troops brought attack dogs and placed snipers on the roofs. He said he saw Israeli tanks and was briefly detained, interrogated and sent on his way. His father and brother are still being held by the Israelis, he said. The last time he saw them, they were wearing plastic handcuffs.

The villagers walked three miles to a shelter, lighting their way with mobile phones, they said. They put the elderly and children on carts and the backs of motorcycles.

The residents of Um Al Nasser are part of the mass evacuation of civilians pouring out of north and east Gaza. The United Nations relief agency said the number of Palestinians seeking emergency shelters doubled in 24 hours. There are now almost 50,000 residents camped in 43 schools, most sleeping on the floors of vacant classrooms.

The men of Um Al Nasser spoke at a boy’s elementary school filled with several thousand people from their town, all Bedouins. Their carts and donkeys crowded the streets out front. Their sheep and goats were abandoned to graze under the rocket and shell barrages.

As they fled their homes, the Bedouin said they heard small-arms fire that could have signaled a fight between Gaza militants and Israeli soldiers. “But you couldn’t see your hand in front of your face with all the smoke,” said Minwer Abu Rafeah, a farmer. The men said they were not involved in the fighting.

Musheer Al Masri, a Hamas politician, said there were clashes near Um Al Nasser early Friday. He confirmed the Israelis have entered the Gaza Strip in force but insisted in an interview, “The Israelis are inside the fence but only tens of meters inside. They found the resistance waiting for them.”

Masri boasted that Hamas cadres have fired Kornet anti-tank guided missiles at Israeli jeeps and tanks, producing casualties that are being hidden by the military from the Israeli public.

Hamas spokesman Sami Abu Zuhri, standing in front of Shifa Hospital, where members of the Islamist militant movement gather to brief — and spin — the media, said, “There have been clashes between us and the Israelis. Serious heavy clashes between the resistance and the Israelis. We have suffered no injuries.”

The Israeli military said their troops have “neutralized 17 terrorists” in the offensive and taken 13 militants who surrendered in for questioning.

Hamas said they will continue to fight until their demands are met. The movement wants the crossing with Egypt opened, back salaries paid, and an end to the blockade that has denied Gaza services such as an airport or seaport.

At the U.N. shelter, people from Um Al Nasser complained that they had no mattresses to sleep on and not enough food to eat.