Three explosions at Egyptian resorts near the border with Israel have killed at least 21 people, although some reports speak of a higher death toll.
Some people are believed to be still trapped in Taba's Hilton hotel
The main blast happened at the Hilton hotel in Taba on the Sinai peninsula, a resort popular with Israelis.
Israeli officials say a vehicle loaded with explosives blew up after ramming the hotel, killing 19 people.
The other blasts hit backpacker beaches near the resort of Nuweiba 60km (38 miles) further south, killing two.
Officials had initially reported at least 30 dead, but by Friday morning they said rescuers had located 19 bodies in the rubble.
An Israeli general says 122 people were wounded in the attack.
Ten floors of Taba's Hilton hotel have collapsed, and it is feared some people may be trapped.
At least two were killed in the other two blasts.
Israel's deputy defence minister Zeev Boim, who is in Taba, said it was too early to say who carried out the attacks, but an attack like this could not have been anticipated.
But he told reporters: "In my personal opinion it seems that it is more fitted to the international terror groups like al-Qaeda or some branches of al-Qaeda."
Taba is the main crossing point between Israel and Egypt, and a major gateway for thousands of Israelis going on holiday to resorts and hotels on the Red Sea.
Many holidaymakers would have been celebrating the last day of a Jewish holiday, Sukkot.
The Israeli government has now told them to get out of Egypt. The BBC's James Reynolds, who is at the border, says he saw hundreds of Israeli tourists walking across the border quietly and sadly, many with tears in their eyes.
Israeli rescue teams with bulldozers have headed across the border towards the hotel to look through the wreckage.
The Hilton hotel is cut off from the outside world by the Israeli border to the north and an Egyptian checkpoint immediately to the south.
The Egyptian authorities have long regarded the eastern Sinai coast, along the Gulf of Aqaba, as less likely terrorist targets than the great monuments along the Nile.
It is a long way across the barren peninsula and security is fairly easily enforced.
At the end of 2000, it hosted the last serious round of peace talks between Israel and the Palestinians. The hotel also attracts Israeli gamblers to its casino.
The other explosions were in Ras al-Shitan, a camping area that is popular with young Israeli backpackers. The site is near the town of Nuweiba, which itself boasts a few hotels and restaurants.
The Israeli authorities said they were sending buses to evacuate any of the 12,000 to 15,000 Israelis in the Sinai who wish to leave.
'People started to run'
Last month, the Israeli government urged its citizens not to visit Egypt, saying there had been a firm threat to tourists there.
Israeli emergency teams are taking part in the rescue, and casualties are being treated in Taba and the nearby Israeli resort of Eilat.
"There are dozens of people on the floor, lots of blood, it is very tense," one witness to the Hilton blast, Yigal Vakni, told Israeli radio.
"I was in the casino when it happened. There was a massive explosion and the left wall came down.
"People started to run around like crazy."
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