More than 50 people have been hurt in clashes between Egyptian police and pro-Palestinian activists seeking to take a convoy of supplies to Gaza.
Protests reportedly broke out when Egyptian authorities at the port city of Al Arish ordered some lorries to go via an Israeli-controlled checkpoint.
British MP George Galloway, leading the convoy, told Reuters that Israel was likely to prevent them entering Gaza.
The activists want all the goods to be sent via Egypt's Rafah crossing.
Some 520 people are travelling with the convoy. Reports suggest about 40 of them and 15 Egyptian police were injured in the clashes.
Reuters news agency quoted a security source saying that the police had used water cannon to force the activists to leave Al Arish harbour after they had occupied it in protest.
Mr Galloway, the sole MP for the Respect party in the British parliament, told Reuters: "It is completely unconscionable that 25% of our convoy should go to Israel and never arrive in Gaza."
Gaza is under a tight Israeli and Egyptian blockade, tightened since Hamas took over the strip in 2007.
The clashes follow an earlier row with the Egyptian authorities over what route the convoy should take to reach Egypt in the first place.
The convoy of nearly 200 trucks is carrying food and other relief supplies for Palestinians in Gaza.
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