(Adds increase in number of arrests)
By Will Rasmussen
CAIRO, Jan 23 (Reuters) - Egypt detained scores of Muslim Brotherhood activists in house raids and street arrests on Wednesday, accusing them of illegally organising protests against the Israeli blockade of Gaza, security sources said.
In Cairo's central Tahrir square, police and plainclothes security men beat fleeing protesters with sticks as they broke up a demonstration of hundreds of people that was led by Islamists and leftists. Six protesters were detained.
"No to the siege of Gaza," protesters chanted. "Break the bonds, remove the barriers," others shouted.
Egypt is under increasing domestic pressure over the situation at the Gaza border. The arrests are the latest in a crackdown on the Brotherhood, Egypt's most powerful opposition group.
A Brotherhood spokesman said security men had detained 87 of its members including 32 in house raids in northern Egypt, where the group has a strong popular base. Another 55 men were picked up from the town of Fayyoum, south of the Egyptian capital.
Those detained include the secretary general of the Cairo doctors' syndicate, Saad Zaghloul, security sources said.
The Brotherhood said the detained men had organised protests on Tuesday and Wednesday. They were accused of organising protests without a permit and belonging to a banned organisation, security sources said.
"There are national demands for Egypt to open the Rafah crossing, the only gateway available for the Gaza Strip," Brotherhood leader Mohamed Mahdi Akef said in a statement.
Israel closed its borders with the Hamas-controlled Gaza Strip last week, cutting fuel supplies to the territory's main power plant and petrol stations and stopping aid shipments. It resumed fuel supplies on Tuesday.
The Rafah border crossing between Gaza and Egypt had been mainly closed since June.
Palestinian militants blew up part of the wall between Gaza and Egypt on Wednesday, and tens of thousands of Palestinians poured into Egypt. Egyptian riot police stood aside.
Israel said the blockade was aimed to make Palestinian militants stop firing rockets into southern Israel. The European Union and international agencies have called the closure a collective punishment of Gaza's 1.5 million people.
The Muslim Brotherhood, a non-violent group that the Egyptian government considers an illegal organisation, says Egypt should unilaterally open the border with Gaza.
Members of the Brotherhood hold a fifth of the seats in parliament and operate openly within limits, although security forces often detain members without formal charges. More than 400 members of the group are currently in detention. (Writing by Cynthia Johnston; editing by Elizabeth Piper)
