By Yasmine Saleh and Shadia Nasralla
CAIRO (Reuters) - Egypt's Muslim Brotherhood called on Saturday for more mass demonstrations in support of ousted President Mohamed Mursi after a huge pro-Mursi march broke up peacefully before dawn, ending a week in which at least 90 people were killed.
The Brotherhood, which has maintained a vigil near a Cairo mosque since before the army removed Mursi on July 3, has said it will not leave the streets until he is restored to power.
Mursi, Egypt's first freely elected leader, has been held incommunicado since he was deposed in what the military says was a justified response to popular demand after millions of people demonstrated against him. The Brotherhood denounces the army coup as a reversal of democracy.
Turmoil in the most populous Arab state has alarmed Western donors. Egypt sits astride the Suez Canal and has a strategically important peace treaty with Israel.
Large crowds of Brotherhood supporters finally dispersed before dawn on Saturday after marching through the streets into the early hours holding up Mursi pictures at traffic lights.
Tens of thousands had turned out on Friday for what the Brotherhood called a "day of marching on".
Mursi's opponents say those demonstrations are still much smaller than the ones that brought Mursi down.
The Brotherhood has showed its organizational muscle and persistence by keeping its vigil running into a third week and bringing in coach loads of supporters from the provinces for big marches, despite summer heat and the Ramadan fasting month.
At one stage, hundreds of demonstrators stood behind barbed wire shouting at soldiers a few dozen meters (yards) away.
"I am here to say 'no' to the military coup and 'yes' to Mursi, who I see as my legitimate president," said Ahmed Adel, a 22-year-old student, in downtown Cairo.
The interim authorities have issued arrest warrants for the Brotherhood's leaders, including Essam El-Erian, who issued the call for more demonstrations on Monday.
"Egypt decides through the ballot box, through protests, mass marches and peaceful sit-ins," Erian said on Facebook.
Friday's demonstration passed off peacefully, in contrast to deadly violence a week earlier when 35 people were killed in running battles between pro- and anti-Mursi demonstrators.
On Monday, 57 people were killed when the army fired on Mursi supporters near a Cairo barracks. The army says it was responding to an attack by terrorists; the Brotherhood says its partisans were massacred.
The United States has refused to say whether the army takeover was a "coup", which under U.S. law would require it to cut off aid including $1.3 billion a year in military support.
In recent days it has described Mursi's rule as undemocratic because of the vast popular protests against him, but also urged the authorities to release him and stop detaining his followers.
Turmoil since a popular uprising toppled President Hosni Mubarak in 2011 has wrecked Egypt's economy, scaring away tourists and investors, draining hard currency reserves and making it difficult to import food and fuel, which the government distributes at heavily subsidized prices.
State news agency MENA said a shipment of 70,000 tons of diesel arrived in Alexandria on Saturday from Turkey and Sweden.
Rich Arab Gulf states Saudi Arabia, the United Arab Emirates and Kuwait, happy at the overthrow of the Brotherhood, have offered Egypt $12 billion in cash, loans and fuel.
Egypt's interim authorities have set out a "road map" to restore full civilian rule, calling for a new constitution and parliamentary elections in about six months, to be followed by a presidential vote.
A judge has been named interim president and a liberal economist, Hazem el-Beblawi, has been appointed prime minister.
He is trying to cobble together a cabinet likely to be made up mainly of technocrats and liberals, without offending a large ultra-orthodox Islamist group that broke with the Brotherhood to accept the military takeover. Beblawi told Reuters on Saturday he expects to name the cabinet within two days.
Egypt's crisis has raised fears over security in the lawless Sinai peninsula bordering Israel and the Palestinian Gaza Strip, where militants attack security forces checkpoints almost daily.
The headline in state-run Al Gomhuria newspaper read: "Sinai's Purification Operation within Days", referring to a possible army offensive against militants in the region.
But a senior army officer, who asked not to be named, said this was unlikely to take place immediately because forces are now focused on keeping the peace during political turmoil.
Security sources said on Saturday a Palestinian had been arrested in Egypt on suspicion of carrying out attacks on a natural gas pipeline.
(Additional reporting by Yusri Mohamed in Ismailia; Writing by Peter Graff; Editing by Alistair Lyon)