By Mubasher Bukhari and Asif Shahzad

LAHORE, Pakistan (Reuters) -Pakistani police have arrested two Christian brothers accused of blasphemy, a spokesperson and a source said on Friday, two days after a Muslim mob burnt churches and houses, blaming the two men for desecrating the Koran.

Pages of the Koran were found in a street with derogatory comments written on them in red, police said. One attached extra page also carried the names, addresses and national identity card numbers of the accused, provincial police chief Usman Anwar said.

Police were investigating all angles as to why the names and addresses would be attached, he told Reuters. A court ordered the two suspects to be held in police custody for seven days for questioning, a government spokesperson said.

Blasphemy is punishable by death in Pakistan but no one has ever been executed. Numerous accused have been lynched by outraged mobs. A former provincial governor and a minister for minorities were shot dead for trying to reform the blasphemy law.

Rights groups say accusations of blasphemy are sometimes used to settle scores. Hundreds of people are languishing in prison after being accused because judges often put off trials, fearing retribution if they are seen as being lenient, they say.

Paramilitary troops have been guarding site of the arson attacks, a Christian settlement in Jaranwala in Faisalabad industrial district, which also includes the historical Salvation Army Church and Saint Paul Catholic Church.

A Christian graveyard was also desecrated, residents and the community leaders said, adding that the mob dragged belongings from Christians' houses and set them on fire.

The violence continued for 10 hours without intervention by police at the scene, residents and community leader said. The police have denied that, saying they prevented even worse damage.

Caretaker Prime Minister Anwar ul Haq Kakar said on Friday that minorities had to be protected at all costs, promising to take action against those involved in violence.

Police said they have so far rounded up 128 people involved in the mob attack.

Residents said thousands of Muslims led by local clerics were seen carrying iron rods, sticks and daggers during the violence.

It started after someone took the desecrated pages of the Koran to a mosque prayer leader, which was followed by announcements calling for punishment, residents and police said.

Residents said clerics from an outlawed Islamist political party - Tehreek-e-Labaik Pakistan (TLP) - led the campaign which resulted in the violence, residents and government sources said.

The TLP denied that, saying it joined the police in calming down the situation.

"We looked into the announcement from the loudspeakers. The same people who were making announcements on loudspeakers later joined us for the peace process," the police chief said.

Hundreds of Christians who fled the settlement have since started returning home, Akmal Bhatti, a community leader, told Reuters.

(Writing and reporting by Asif Shahzad in Islamabad; Editing by Kim Coghill and Nick Macfie)