Israel has completely sealed off the Palestinian territories for fear of possible attacks during the Jewish Passover holiday, which starts at sunset on Wednesday.
Israel said the closure would remain in effect at least until Sunday
The Israeli army said it had received warnings of attacks and that Palestinians from the West Bank and Gaza Strip would not be allowed to enter Israel.
Gaza's Mediterranean shores would be closed to fishermen, and crossings between the West Bank and Jordan, and between Gaza and Egypt, would also be closed, the army said.
Israel fears that Palestinian militants will carry out attacks on the anniversary of last year's Passover suicide bombing in the Israeli seaside resort of Netanya, in which 29 people were killed.
The bombing - by Palestinian militant Abdel Basset Odeh - was single deadliest attack since the Palestinian uprising, or intifada, began in September 2000.
Meanwhile, three Israelis and four Palestinians were killed in the West Bank and Gaza, as violence continued on Tuesday.
In Nablus on the West Bank, an Israeli officer and a Palestinian militant were killed in a shoot-out. Another suspected militant was killed when he refused to surrender, the Israeli army said.
In the Gaza Strip, a Palestinian gunman hurled hand grenades and sprayed automatic weapons fire at the Karni crossing point, killing two Israeli workers before being shot dead, the army said.
Another Palestinian militant was killed by Israeli troops in the Gaza town of Rafah.
On high alert
Hundreds of police and volunteers are stepping up security in Israel during the week-long Passover holiday, the Israeli Ha'aretz newspaper reports.
Mainly diners were killed in last year's Passover bombing
Special attention will be paid to guarding shopping centres, outdoor markets, bus stations and beaches, as well as synagogues, the paper says.
Israeli security forces also set up roadblocks on Tuesday night around Jerusalem, after receiving warnings of imminent attacks, Israeli Army Radio said.
Palestinian security sources were quoted by the Associated Press news agency as saying that they had been informed that the closure would take effect from Wednesday at 0300 local time (0000 GMT).
An Israeli army spokesman said the closures would remain in effect at least until Sunday.
Similar measures were taken by the Israelis last month during the Jewish festival of Purim.
'Death penalty merited'
On Monday, an Israeli military court sentenced four Palestinians to life imprisonment over last year's Passover attack, in which Odeh blew himself up in Netanya's Park Hotel as a group of mainly elderly people attended a festival meal.
The four defendants and bomber Odeh were members of Hamas
The four - Fathi Khatib, Nasser Watimi, Mohammed Schreim and Muammar al-Sheikh, all from the West Bank - were convicted of helping Odeh to carry out the attack.
They were handed 29 life sentences each, plus another 20 each for planning to carry out another suicide attack.
Odeh and the other four were all members of the Islamic militant group Hamas.
In passing sentence, some of the judges said this was a case that merited the death penalty, but it was not invoked.
The four defendants blamed the Israeli "occupation" for their actions. One said at the outset that he did not recognise the authority of the military court.
Prime Minister Ariel Sharon's office said on Monday that Israel had now tracked down all those involved in the Netanya attack.
Five had been arrested and three had been killed, officials said.