Seven Israeli tanks entered the northern part of the Gaza Strip, near the town of Beit Hanun, on Tuesday, witnesses and members of Gaza's security forces said.
The tanks, which entered around 400 metres into the Strip, were accompanied by a bulldozer, but it was unclear whether a demolition was planned.
Israel has often demolished structures and cleared land along Gaza's border with its state, under the pretext of security concerns.
An Israeli military spokesman told AFP he could neither confirm nor deny any incursion.
Israel and Hamas are formally committed to a truce agreed after Israel's devastating 22-day Operation Cast Lead, which ended in January 2009.
But in recent months, resistance groups have fired dozens of rockets into southern Israel, prompting retaliatory airstrikes by the Israeli military.
A new Save the Children report warned that Gaza's children were increasingly fired at by Israeli soldiers while they scavenge in remnants of building destroyed during the Israeli 2009 invasion, Al-Jazeera said.
Israeli troops shot twenty-six children near the border last year, a UNICEF-led group said.
Sixteen of these children were shot outside of Israel's so called "exclusion zone" which extends 300 metres into Gaza.
The ongoing Israeli blockade forces the children to scavenge for construction material intentionally made unavailable to the Strip, according to the report.
Preventing construction material from entering has chronically impeded the rebuilding of thousands of homes destroyed during the war.
"Because of the blockade's devastating economic impact, children are being forced to work and scavenge near the fence. Even those who are not in the so-called 'buffer zone' unilaterally imposed by Israel are being targeted by Israeli soldiers," Chris Gunness, spokesman for UNRWA was quoted in Al-Jazeera.
The Israeli blockade was condemned in the report for forcing children to drop out of school to take up work and "ravag[ing] the economy, leaving many ... struggling to support their families."