Egypt closed its border with the Gaza Strip on Tuesday, said a security official, after opening it for three days to allow Palestinians to leave the Hamas-ruled territory for medical treatment. Since Saturday, 1,433 Palestinians crossed from the besieged Gaza Strip into Egypt, said the official. Since Hamas seized power in Gaza 11 months ago, Israel has sealed Gaza to all but very limited humanitarian assistance. For months, Hamas has been calling on Egypt to open the Rafah border crossing - the only gateway to Gaza not under Israeli control - but it has done so on only a few occasions since last summer. In January, Gaza militants blew open large sections of the border fence, sending hundreds of thousands of Palestinians pouring into Egypt to stock up on basic goods before it was resealed a few days later.