Some 40,000 Palestinians are expected to march along the Gaza Strip's border in protest of Israel's economic embargo on the coastal territory.
"Israel will defend its territory and will stop any infiltration attempt into its sovereign borders," Defense Minister Ehud Barak and Foreign Minister Tzipi Livni said in a joint statement sent to all Israeli embassies and missions.
"Hamas is behind activities that place the civilian population on the front lines," the statement added.
The Israel Police will heighten security across the country on Monday, as intelligence officials warned that tens of thousands of Gazans were planning to form a human chain from Rafah to the Erez border crossing as early as 10 A.M. on Monday.
The Israel Defense Forces has already beefed up troops along the border, in preparation for the march, expected after gasoline ran out in Gaza over the weekend.
A large number of police forces will be deployed to join the IDF in the southern district, in case the protest gets out of hand.
The head of the Palestinian Popular Anti-Siege Committee protest, Jamal al-Khudary, said: "We do not have intentions of approaching the fence, either in the north or the south. We hope all the participants will abide by the instructions and we will try to prevent any violations."
He also said the protesters would not try to confront IDF troops.
An official Hamas source maintained that the mass flow towards the border - which will comprise Palestinian women and children - would be spontaneous and was not based concrete plan.
However, he added that the next time Gaza residents decide to rally the economic embargo, the protest would be held only on the border with Israel, and not the border with Egypt.
A security source in Jerusalem said the army was preparing for "all scenarios" ahead of Monday's protest.
"Obviously, if gunmen start shooting at the fence we will have to respond in kind and we are absolutely unwilling to countenance a situation where the fence is breached like it was at Rafah," the source said.
IDF troops on the border have been issued special open fire orders in order to stop even a small number of protesters from crossing the fence, and the army has demarked especially sensitive areas.
If necessary, IDF artillery will fire warning shots at open areas, and should the protestors continue their advance, troops will employ riot dispersal methods.
As a last resort, snipers will open fire at protestors legs. The orders were approved by senior General Staff officers as well as Defense Minister Ehud Barak.
The IDF also said that all Gaza crossings would be closed Monday, including to foreign nationals and journalists.
The gasoline shortage was the result of limitations imposed by Israel on imports into the Strip, excluding fuel for emergency vehicles. Diesel fuel is also said to be in short supply.
Israel's concerns are based on the breach of the Gaza-Egyptian border a month ago, when hundreds of thousands of Palestinians streamed across Rafah into Egypt after Hamas blew up the wall there.
Israel believes Hamas is now planning a new action, directed at Israel, to break the siege on the Gaza Strip and draw global attention to the plight of Gaza's impoverished residents.
Two Qassams fired from Gaza, one strikes western Negev
Palestinian militants in Gaza on Sunday fired two Qassam rockets at southern Israel, Army Radio reported.
One of the rockets struck an open field in the western Negev and the other landed in Palestinian territory. No injuries or damages were reported in either incident.
Also on Sunday, IDF forces uncovered five tunnels used for weapons smuggling during an operation in Dahaniyeh, in the southern Gaza Strip.
Meanwhile, three Palestinians were killed Saturday afternoon in an Israel Air Forces strike on Beit Hanun in the northern Gaza Strip. Sources in the Strip said the dead were civilians. The IDF said the three had been observed attempting to launch a mortar shell at Israel.
Two armed Palestinians were also killed in other incidents in the Gaza Strip.
Hamas declared Saturday as an international day of protest against the siege. Anti-Israel rallies were held in a number of Arab and European countries. Thousands of Palestinians attended the main demonstration in Gaza City, marching to the United Nations headquarters. The IDF deployed a number of battalions near the fence in the northern Strip to prepare for possible Palestinian attempts to breach the border.
The IDF Gaza Brigade has been conducting exercises simulating mass civilian marches, outfitting the soldiers with riot-control gear. The army is concerned that Palestinians may try to take over crossings on the Israel-Gaza Strip border, and that Hamas intends to march them into a Jewish community near Gaza.
Military sources cite the "Hezbollah precedent": The sign that the buffer zone in southern Lebanon was collapsing on the eve of the IDF's withdrawal in May 2000 came when the Southern Lebanese Army abandoned the Taybeh post and hundreds of unarmed Lebanese civilians marched on it.
Meanwhile, Gaza residents Saturday told Haaretz that their cars are "stuck" and they are using taxis or wagons hitched to donkeys. "At most of the gas stations you can't find diesel either," Imad, a Gaza resident, said.
Security officials told Haaretz they are meeting their pledge to the Supreme Court to transfer fuel for emergency vehicles, approximately 75,000 liters a week.
A delegation of Hamas and Islamic Jihad members met over the weekend with representatives of Egyptian intelligence in El Arish to discuss opening the Rafah border crossing. This was their third meeting in the past 10 days. News agencies reported that the Egyptians told the Palestinians that they will thwart any more attempts to rush the border.
A Hamas spokesman in the Strip, Ayman Taha, said that the parties had reached an understanding regarding the expected release today of 105 Palestinians arrested by the Egyptians in Sinai. Those arrested were apparently mainly armed activists.