CAIRO (AP) - Tens of thousands of supporters of Egypt's Islamist president rallied on Friday along a main boulevard near Cairo's Presidential Palace in a show of force against opponents demanding his ouster amid increasing tension and polarisation in Egypt.

With pictures of President Mohammed Mursi, Quranic chants over loudspeakers and shouts of "Islamic, Islamic in the eye of the secularists", the rally indicated that Mr Mursi's backers and his Muslim Brotherhood apparently seek to give a religious flavour to the nation's deep political differences.

"I am here to support the legitimacy of an elected president who was chosen by the people through the ballot box," said Mr Saad Ismail, 43-year-old teacher from the Nile Delta city of Beheira.

"We want to ensure the Islamic identity of Egypt," he added. "The majority of people want to be ruled by the Islamic rule."

Nearby, a banner read: "Our battle is an identity battle, against communism and secularism."

Friday's pro-Mursi rally was meant to counter plans by his opponents to stage mass demonstrations on June 30 - the anniversary of his coming to power in 2012 - to demand that he step down. Mr Mursi was elected after a popular uprising ousted former president Hosni Mubarak in 2011.

The June 30 protest campaign is rooted in a months-long petition drive. Organisers announced on Thursday that they have collected up to 15 million signatures supporting early presidential election and Mr Mursi's ouster.

In the run-up to the anniversary, protests and clashes have spread across the country over Mr Mursi's appointment of 17 new governors, 10 of them members of his group. In a particularly striking move, a member of an former militant group was named governor of the ancient city of Luxor. The city witnessed killings of tourists in 1997 at the hands of the militant group, which at the time was led by the newly appointed governor.

Earlier this week, protesters in Luxor and elsewhere used chains to lock up offices of the new governors, sat fire to car tires, and clashed with Brotherhood supporters.

Mr Mursi's year in power has been marred by constant political unrest and a sinking economy. His opponents charge that he and his Brotherhood have been systematically amassing power, excluding liberals, secular groups and even ultraconservative Salafi Muslims.

A persistent security vacuum and political turmoil have frightened away foreign investors and tourists. Egypt's already-battered economy has continued to slide, draining foreign currency reserves and resulting in worsening fuel shortages and electricity cuts along with increasing unemployment. All of these factors have added to anti-Mursi sentiments, further polarising the nation.

His backers charge that the opposition, having lost elections, is trying to impose its will through street protests. Their counter-campaign is taking on increasingly religious tones.

A 20-year-old veiled university student Doha Abdel-Salam said she joined the rally to denounce calls for secularism by "those who are supposed to be intellectuals".

"So, it is very clear there is a war on Islam," Ms Abdel-Salam said, adding she came not to defend Mr Mursi or the Brotherhood, but "to defend my religion".

Even though Friday's gathering was dubbed "one million people rally against violence", it was accompanied by religious edicts from pro-Brotherhood clerics who gave the green light to fighting with Mr Mursi's opponents, describing the opposition's June 30 protests as "religious war".

On Thursday, a leader of the radical Islamist Gamaa Islamiya party Assem Abdel-Maged told a gathering in the southern city of Minya that those conspiring against Mr Mursi include Coptic Christian extremists, communists and remnants of Mubarak's regime.

"Our deaths are in heaven, and their deaths are in hell," Mr Andel-Maged said.

Meanwhile, Mr Ashraf Abdel-Moniem, a preacher and member of the pro-Mursi Islamist umbrella - known as the Religious Legal Commission for Rights and Reform - said that killing those who take up arms against Muslims on June 30 is permissible.

In a video circulated on social networking sites, he said "those who raise an arm against Muslims and threaten them with death or fight them or kill them, they have no sanctity, and it is even a duty to push them back, even by killing them if they don't retreat".

However, Mr Mursi's hardline Islamists were snubbed on Thursday when Sheik Ahmed el-Tayeb, the grand imam of the Al-Azhar Mosque in Cairo, said that peaceful protests against the President were permitted.

Al-Azhar is the Sunni Muslim world's foremost seat of learning, and styles itself as a voice of moderation. With the political rise of ultraconservatives since Mubarak's fall in February 2011, Sheik el-Tayeb and other leading Al-Azhar clerics have actively pushed back against their strict interpretations.