CAIRO, Sept 17 (Reuters) - Police hunted a veteran member of a former militant group in southern Egypt on Tuesday, security officials said, after he fled a town where the army and police deployed on Monday in an attempt to reimpose state authority.

Assem Abdel Maged of the Gamaa Islamiya is among several dozen Islamist activists sought by the police in Minya province after their operation on Monday to restore control over the town of Delga, some 300 km (190 miles) south of Cairo.

The town had slipped from the state's grip following the July 3 downfall of President Mohamed Mursi, a Muslim Brotherhood member. Minya has witnessed some of the most intense violence since then: around 70 people were killed there on Aug. 14, the day police broke up pro-Mursi protests in Cairo.

At least 20 churches were attacked in the province in the days that followed. Many of them were torched.

Abdel Maged, who spent 25 years in jail for a role in the 1981 assassination of President Anwar Sadat, emerged as a public figure after the 2011 downfall of Hosni Mubarak. He once shared a cell with al Qaeda leader Ayman al-Zawahri.

Ahead of mass protests against Mursi, Abdel Maged appeared at a Brotherhood rally where he told the crowds to push for a pure Islamic state if Mursi was toppled.

"We have information that he is in Minya. We are pursuing him and, God willing, we will get him soon," a senior official in Minya said, speaking on condition of anonymity in line with ministry regulations.

LUXOR ATTACK

Gamaa Islamiya, notorious for a 1997 attack that killed 58 tourists in Luxor, renounced violence more than a decade ago. It set up a political party after Mubarak's downfall and drew closer to Mursi in the last months of his rule as the Brotherhood deepened its ties with the religious right.

Witnesses said the police and army were still deployed heavily in Delga. Army helicopters flew overhead. Security forces removed makeshift barriers erected by Mursi supporters on the roads leading into the town.

Several hundred Mursi supporters protested against the army as night fell on Tuesday, chanting "The coup is terrorism!" and "Delga is the symbol of steadfastness!".

A local Coptic church official, Anba Aghabious, said Christians were still being harassed by Islamist hardliners in Delga, a town of around 200,000 people. "They are threatening them on the grounds that they are the cause of the police and army showing up," he said by telephone.

Egypt's Coptic Christians, who make up 10 percent of its 85 million people, have coexisted with the majority Sunni Muslims for centuries. Violence erupted periodically, especially in the impoverished south, but the wave of violence targeting Christians last month was the worst in years.

A local Brotherhood official said detainees were being held in a Delga police station that had been abandoned in the violence but had now been partially repaired. Speaking by telephone, he said the security forces were detaining anyone who took part in pro-Mursi protests. (Reporting by Omar Fahmy; Editing by Kevin Liffey)