* Christians say officials block building despite permit
* One killed, 35 wounded in Giza clashes
* Some Muslims join violence
(Adds Muslim-Christian clashes, analysts)
By Patrick Werr
CAIRO, Nov 24 (Reuters) - Clashes between riot police and hundreds of Christians protesting after the authorities halted construction of a church in Cairo took a sectarian turn on Wednesday when dozens of Muslims joined the violence.
One Christian was killed and dozens were wounded in scuffles when Orthodox Copts hit the streets and hurled stones at police lines. Some officers threw stones back. Muslims also lobbed rocks at the Christian protesters from the security cordon.
Christian protests on this scale are rare in Muslim-majority Egypt, but sectarian tensions have risen. Analysts say the state must address grievances such as those over laws making it easier to build a mosque than a church to prevent an escalation.
The protest erupted four days before Sunday's parliamentary election, which has also led to scattered unrest.
"These events reflect pent-up sectarian frustrations in Egyptian society that have become more inflammatory because of the election battle," said Nabil Abdel-Fattah, an analyst at al-Ahram Centre for Political and Strategic Studies.
The Health Ministry said a 19-year-old man was killed and 35 people were wounded, including 13 security men. Medical and security sources had previously said 45 people were hurt.
The Interior Ministry said at least 112 protesters were detained in the Giza area of the capital, where the authorities had halted construction of a church although the Copts said they had an official permit.
"We will build it, we will build it," chanted some of the protesters near the unfinished church.
Some Christians, who make up 10 percent of Egypt's 79 million people, demonstrated near the church and others near the Giza governor's office. The state news agency MENA said up to 3,000 people had been involved in the protest.
One Reuters picture showed a demonstrator hurling a petrol bomb towards police. Other images showed police breaking up brick slabs on the street into a size that could be thrown.
Scores of police sealed the area and fired tear gas.
"Look, this is our government throwing rocks at us. All this because of a church," said 30-year-old Samuel Ibrahim, pointing to police throwing rocks at protesters.
SLOW RESPONSE
Mustapha al-Sayyid, political science professor at Cairo University, said it was not the first time such disputes had led to violence. "The state has been slow to deal with it," he said.
"A law has been proposed to unify the application process for building places of worship for both Christians and Muslims. But I don't know when it will be presented to parliament."
Giza governor Sayyed Abdel-Aziz said the Christians appeared to have misused a permit for a social centre to build a church.
"I am completely willing to help Christian leaders get the permit for a church, but they have to stop turning it into a church without authorisation," he told MENA.
The Christians said they had the right permit and would continue to build the three-storey domed structure.
Egypt's Christian and Muslim clerics emphasise sectarian harmony, but communal tensions sometimes erupt into violence, often sparked by land disputes or cross-faith relationships.
"We have been warning about the government's failure to deal with the rising sense of injustice by the Christian community for a long time. This is an extremely disturbing development," said rights campaigner Hossam Bahgat.
His group, the Egyptian Initiative for Personal Rights, reported in April that the number of violent sectarian incidents had risen to 53 in 2009 from 24 in 2008, saying many cases had been insufficiently investigated or ignored.
The public prosecutor said investigators were on the scene of Wednesday's clashes.
"Today we are talking about security forces using excessive forces with peaceful protestors demanding their constitutional right to freedom of worship," said Bahgat. (Additional reporting by Dina Zayed and Sarah Mikhail, writing by Edmund Blair;editing by Alistair Lyon and Samia Nakhoul)
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