On Sunday morning, June 25, about 20,000 Muslims are expected to congregate at Angel Stadium in Anaheim to pray together and celebrate Eid al-Fitr, the day that marks the end of the holy month of Ramadan.

This year, the biggest concern for this event — and other end-of-Ramadan festivities — is security.

On Monday, the Council on American-Islamic Relations issued an alert to all mosques and Islamic organizations nationwide, warning them to be vigilant after incidents of violence against Muslims in recent weeks and a year punctuated by an increase in anti-Muslim hate crimes, hate incidents and rhetoric.

CAIR-LA has issued a similar alert for all mosques in Southern California, said executive director Hussam Ayloush.

“We’re asking mosque administrators to make sure the areas are well-lit and there’s adequate security available,” he said.

Ayloush also is asking Muslims not to engage with people who target them through hate speech.

“Don’t respond to racial slurs because you don’t know the state of mind of that person,” he said. “The best thing to do is to ignore. If you feel unsafe, call the police and move to a safe place immediately.”

Ayloush said two recent incidents — the murder of 17-year-old Nabra Hassanen of Reston, Va., who was killed after leaving her mosque Sunday morning, and an incident outside a mosque in Finsbury Park, London, where a man plowed a rented van into worshipers, leaving one dead and nine others injured — have left American Muslims shaken.

The community is certainly more concerned this year, said Ahsan Baseer, board president of the Islamic Society of Corona-Norco.

“We have told everyone to be alert and have especially warned girls and women wearing hijabs not to walk by themselves,” he said. “It’s unfortunate that we have to do this, but these are precautions we have to take under current circumstances.”

Baseer’s mosque will host an Eid event this weekend at Santana Regional Park in Corona. About 4,000 people attend each year, Baseer said.

“We’ll have our usual security for that event,” he said. “We’ve also requested additional police patrols.”

The prayer at Angels Stadium will be held inside, on the grass, instead of out in the parking lot as was done in September for the Eid al-Adha event, said Nicole Alhakawati, one of the event’s organizers.

“In the past we’ve had hecklers and protesters at our events,” she said. “We’ve never had any violence so far. But, we’re really taking steps to make sure everyone is safe.”

In addition to moving the event inside the stadium for increased security, organizers are requiring free tickets to be issued by mosques and organizations in order for participants to be allowed entry.

Alhakawati said members of three of the region’s largest mosques — the Islamic Institute of Orange County in Anaheim, the Islamic Society of Orange County in Garden Grove and the Islamic Center of Irvine — are expected to participate in the mass prayer, in addition to several other organizations.