Australian police said on Thursday they had launched an investigation after a threatening letter was sent to the country’s largest mosque, the third such incident in the lead-up to the Muslim fasting month of Ramadan.

The letter sent to Lakemba Mosque in Sydney’s west on Wednesday contained a drawing of a pig and a threat to kill the "Muslim race", local media reported.

Police said they had taken the letter for forensic testing, and would continue to patrol religious sites including the mosque, as well as community events.

The latest letter comes weeks after a similar message was mailed to the mosque, depicting Muslim people inside a mosque on fire.

Police have also arrested and charged a 70-year-old man in connection with a third threatening letter sent to Lakemba Mosque's staff in January.

The Lebanese Muslim Association, which runs the mosque, told the Australian Broadcasting Corp (ABC) it had written to the government to request more funding for additional security guards and CCTV cameras.

Some 5,000 people are expected to attend the mosque each night during Ramadan. More than 60% of residents in the suburb of Lakemba identify as Muslim, according to the Australian Bureau of Statistics.

Bilal El-Hayek, mayor of Canterbury-Bankstown council, where Lakemba is located, said the community was feeling "very anxious".

"I've heard first-hand from people saying that they won't be sending their kids to practice this Ramadan because they're very concerned about things that might happen in local mosques," he said.

Prime Minister Anthony Albanese condemned the recent string of threats.

"It is outrageous that people just going about commemorating their faith, particularly during the holy month for Muslims of Ramadan, are subject to this sort of intimidation," he told ABC radio.

"I have said repeatedly we need to turn down the temperature of political discourse in this country, and we certainly need to do that."

Anti-Muslim sentiment has been growing in Australia since the war in Gaza War in late 2023, according to a recent report commissioned by the government.

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The Islamophobia Register Australia has also documented a 740% rise in reports following the Bondi mass shooting on December 14, where authorities allege two gunmen inspired by Islamic State killed 15 people attending a Jewish holiday celebration.

"There's been a massive increase post-Bondi," Mayor El-Hayek said. "Without a doubt, this is the worst I have ever seen it. There's a lot of tension out there."