The Matahen checkpoint has been set up just north of the town of Khan Yunis, dividing the Southern Gaza Strip from the Central Gaza Strip, Palestinian sources said.
Israeli forces shot at travellers attempting to make their way across this checkpoint, killing one man, and injuring another.
Further north, travellers have been forced to ride on donkey carts or walk the three kilometres of sand and rocks to make their way across the second, newly erected barrier dividing the northern Gaza Strip and City from the Central Gaza Strip, near the Gaza seashore, eyewitnesses told Aljazeera.net. No vehicles have been allowed through.
"I'm young, and I should have more energy, but my feet feel like they have pins in them from walking so much in this heat," said Hanan Abu Saad.
"Now think of all the sick people and the elderly that are trying to make it to the hospitals. It's a catastrophe, it really is."
Abu Saad said Israeli occupation troops shot at a group of travellers who attempted to walk on the asphalt road instead of the sand and rocks below.
"There was a shower of bullets - we all ducked," said one witness.
Palestinians regularly face
humiliation at checkpoints
"If I didn't have final exams in college, I wouldn't even be here," said another frustrated young woman.
Several elderly women could be seen taking a rest from their journey.
The closure has stalled employees, college students, and patients from making their daily commute to Gaza. Human rights organisations have called the internal closure an act of collective punishment.
The closure follows a deadly Palestinian strike against an Israeli military outpost near the illegal settlement of Gush Katif in the central Gaza Strip, which killed one occupation soldier and injured five others.
Immediately following the attack, Israeli helicopter gunships fired 10 missiles at the Zaytun neighbourhood in Gaza City. The strikes, which echoed throughout the city and lit up the night sky, destroyed a foundry and injured Palestinian bystanders.
"The response is coming - all I will say
is that the entire leadership [of Hamas] had better beware"
Eitan Arusy, Israeli army spokesperson
Israeli army spokesperson Eitan Arusy told Aljazeera.net: "The response is coming - all I will say is that the entire leadership [of Hamas] had better beware."
Two Palestinians from Khan Yunis, to the south of the outpost, were killed by Israeli forces shortly after the attack, and another six were injured, according to Palestinian medical sources. One of the victims was an 11-year-old boy.
Another young boy was injured by Israeli gunfire in Rafah in the southern Gaza Strip.
Eight Palestinian homes were also demolished north-west of the Qarara quarter of the Central Gaza Strip.
Meanwhile, Israeli tanks took position at the entrance to the northern Gaza Strip town of Bait Hanun early on Monday afternoon, eyewitnesses said.