By Kanupriya Kapoor

JAKARTA (Reuters) - Indonesian President Joko Widodo and his vice president called for peace as tensions rose on Thursday ahead of a protest planned by hardline Muslim groups against the Jakarta governor, a Christian and the first ethnic Chinese in the job.

The groups claim that Governor Basuki Tjahja Purnama, popularly known as "Ahok", had insulted the Koran and was guilty of blasphemy. They plan a protest rally on Friday.

Security has been tightened in Jakarta, a sprawling city of 10 million, and police have deployed armored vehicles and armed personnel as the plan stoked religious and ethnic tensions in the world's largest Muslim-majority nation.

"Everything and everyone should continue to work as normal, schools should run as normal," Widodo said in a joint statement with Vice President Jusuf Kalla.

Kalla added: "The government will listen to all opinions...but I believe because the protest will be carried out on Friday, a holy day, protesters will be respectful. That is our hope."

But some businesses have told employees to stay home on Friday, citing fears that violence could erupt during the rally.

Police said dozens of social media accounts had been found "publishing provocative statements and images" and urging people to take violent action in the name of Islam against Purnama, including calls to kill him.

"We have seen racially and ethnically divisive statements being spread online and there are indications many of them are anti-Chinese," said Jakarta police spokesman Awi Setiyono.

Ethnic Chinese make up just over one percent of Indonesia's 250 million people, who are overwhelmingly Muslim. Typically, Indonesian Chinese do not enter politics, but Purnama has been a close ally of Widodo for decades.

He was the deputy governor of Jakarta when Widodo was governor and took over when Widodo stepped down in 2014 to contest the presidency.

Critics say Widodo's government is doing little to contain the increasingly hostile rhetoric against Purnama from hardline Muslim groups. The mounting religious and ethnic tensions come ahead of next year's election for Jakarta governor in which Purnama has said he will be a candidate.

"This theater of hatred will continue if (Widodo) doesn't tackle it and Indonesia will be a different country with less tolerance and more persecution of minorities," said Andreas Harsono of Human Rights Watch.

Muslim groups have accused Purnama of blasphemy after he said his opponents had deceived voters by attacking him using a verse from the Koran. Police are investigating the case against Purnama, who has apologized for the remarks.

Widodo has vowed not to interfere in the legal proceedings against Purnama, according to the Indonesian Clerical Council, a Muslim group.

"The president has said he has instructed (police) to process the investigation and that he will not intervene in this matter," council member Ma'aruf Amin told reporters after meeting Widodo earlier this week.

BLASPHEMY LAWS

Police are stepping up patrols and online monitoring in a "show of force" ahead of Friday's rally. About 18,000 police and military personnel will be deployed on the day of the protest.

Armored police trucks and armed troopers stood outside the governor's office at City Hall and outside the presidential palace, where thousands of protesters are expected to march on Friday.

A spiritual leader for the protest organizer, the Islamic Defenders Front (FPI), insisted its actions on Friday would be peaceful.

"This is not anti-Christian or anti-Chinese action," Habib Riziek said.

The group has had a history of vigilante attacks and raising complaints of blasphemy against religious minorities since it was formed in 1999. It has also frequently protested against Purnama.

Blasphemy cases were rare during former strongman president Suharto's 32-year reign, when there was little tolerance for hardline religious groups.

But cases have spiked in the country's democratic era after Suharto's fall in 1998, raising fears of increased persecution of minorities.

"If Ahok is taken to court, it will be the most high-profile blasphemy case in Indonesia's history because of his status as a government official," rights activist Harsono said.

"It will create a precedent of more hatred against Christians, against Chinese and other targets."

Indonesia recognizes six religions and a vast majority of the population practice a moderate form of Islam. But Indonesian Chinese have faced persecution and violence in the past, especially during the political and social turmoil that gripped the capital when Suharto was toppled.

Hundreds of people were killed during the 1998 violence and thousands of ethnic Chinese fled the country as mobs rampaged through Jakarta, looting and burning Chinese-owned shops and houses.

Communications Minister Rudiantara said the government is working to counter the online "hate speech".

"Indeed, social media is contributing to the current situation," he said. "The president has made it clear Indonesia's unity is non-negotiable."

The race to lead Jakarta, a sprawling city of 10 million, is often hotly contested, with top political parties jostling to get their candidates elected to a job that is seen as a stepping stone to higher political office.

One of Purnama's rivals in the governor's race is the son of former president Susilo Bambang Yudhoyono.

Purnama, who has gained a reputation as a tough reformer, remains a frontrunner in opinion polls.

(Additional reporting by Angie Teo and Agustinus Beo da Costa; Editing by Bill Tarrant and Raju Gopalakrishnan)