Egypt turned back 450 travellers seeking to cross from Gaza at the Rafah border point after an attack on a Sinai police station, Hamas officials said on Sunday.
Gaza's Hamas-run interior ministry said that the 450 would-be travellers, some of them patients seeking medical treatment, were turned back at the border on Saturday.
Palestinians in Gaza have accused Egypt of creating unnecessary hold-ups at the crossing, the only one open to residents of the coastal territory, and the interior ministry said it had a backlog of some 30,000 travel applications.
In a statement, the ministry gave no details on why the travellers were turned back, but the incident came after Egyptian forces arrested 12 men, including three Palestinians, in connection with an attack on a north Sinai police station.
North Sinai security chief Saleh al-Masri announced the arrests on Saturday, a day after the attack on the police station in El-Arish.
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The attack came as clashes rocked the town on Friday, killing three civilians, an army officer and a police officer and leaving 19 people wounded.
Also on Friday, around 150 men in trucks and on motorbikes rampaged through El-Arish, firing assault rifles in the air, terrifying residents.
They rode through the deserted streets waving black flags which read "There is no God but Allah," before attempting to storm the police station.
Gaza residents hailed Egypt's decision to reopen the Rafah border crossing in May, after an uprising overthrew the government of former president Hosni Mubarak.
The decision ended Egypt's cooperation with a blockade Israel imposed on the Palestinian enclave in 2006, after Gaza-based militants snatched an Israeli soldier.
But since the border reopened, Egypt has closely restricted the number of travellers able to cross each day, leading to repeated requests from Palestinians including the Gaza-based Hamas government for larger travel quotas.