* First violence in weeks in Cairo's Tahrir Square
* Clashes started at event to honour "martyrs" of uprising
* At least four civilians, 48 police hurt, nine arrested
(Adds detail on casualties, quotes)
By Patrick Werr and Yasmine Saleh
CAIRO, June 29 (Reuters) - Police in central Cairo fired tear gas on Wednesday at hundreds of mainly young stone-throwing Egyptians demanding that trials of former senior officials from the discredited Mubarak era proceed faster.
Clashes broke out late on Tuesday in an area of the capital where some families of the more than 840 people killed in the uprising that led to President Hosni Mubarak's overthrow in February held an event to honour those dead.
Youths said police clashed with them during the event to honour "martyrs", the term used to describe those killed in protests. The Interior Ministry said it intervened when a group that was not invited tried to barge into the gathering.
At least 41 policemen and four civilians were injured in the violence that continued into Wednesday in Tahrir Square and near the Interior Ministry, the state news agency MENA said.
Early in the morning young men, many stripped to the waist, were still hurling stones at police near the ministry as commuters went to work. Some ordinary Egyptians said those involved were bent on battling police rather than protesting.
By early afternoon on Wednesday, the crowds around the ministry had been dispersed. Eight ambulances were in Tahrir and the police had left the square.
The clashes were the first such violence in weeks in Tahrir, the centre of the revolt that led to Mubarak being toppled.
"The people are angry that the court cases against top officials keep getting delayed," said Ahmed Abdel Hamid, 26, a bakery employee who was at the scene overnight. He carried stones in his hands.
More Egyptians gathered in Tahrir on Wednesday angered by the way the police handled the crowd overnight.
"I am here today because I heard about the violent treatment of the police to the protesters last night," said Magdy Ibrahim, 28, an accountant at Egypt's Banque du Caire.
Some young men lit car tyres in the street near the ministry, sending black plumes of smoke into the air.
MENA, citing a security source, said nine people were referred to the military prosecutor for investigation on suspicion of stirring up the violence.
First aid workers treated people mostly for inhaling tear gas. A Reuters correspondent saw several people overnight with minor wounds, including some with cuts on their heads.
"NO JUSTIFICATION"
The ruling military council said in a statement on its Facebook page that the events "had no justification other than to shake Egypt's safety and security in an organised plan that exploits the blood of the revolution's martyrs and to sow division between the people and the security apparatus."
Political activists who have helped organise other recent protests in Tahrir said the angry scenes on Tuesday evening and early Wednesday were not part of any planned protest.
Streets were strewn with stones and bricks. One motorbike near the square was spewing black smoke after being set alight.
A hospital in nearby Munira received two civilians and 41 policemen with wounds, bruises and tear gas inhalation, the state news agency said. All were discharged except one civilian with a bullet wound and a policeman with concussion, it said.
Former interior minister Habib al-Adli has been sentenced to jail for corruption but he and other officials are still being tried on charges related to killing protesters. Police vehicles were stoned by protesters at Sunday's hearing.
Police used batons, tear gas, water cannon and live ammunition against protesters in the first days of the 18-day uprising before they were ordered off the streets and the army moved in. Mubarak then handed power to an army council.
The former president, now hospitalised, has also been charged with killing protesters and could face the death penalty. Mubarak's trial starts on Aug. 3. (Writing by Edmund Blair; editing by Mark Heinrich)
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