Muslim community leaders in the UK are calling banking giant HSBC 'Islamaphobic' after they received letters telling them that their banking services will be terminated in September.

Three organizations—The Cordoba Foundation, the Ummah Welfare Trust (UWT), and the Finsbury Park Mosque—have all received nearly identical letters (pdf) from the bank, and two of them believe the cause may be their support of Palestine.

The letters said that the groups fall 'outside' of the bank's 'risk appetite', but gave no further reason for the termination of service.

"For us it is astonishing - we are a charity operating in the UK, all our operations are here in the UK and we don't transfer any money out of the UK. All our operations are funded from funds within the UK," Mohammed Kozbar, chairman of the Finsbury Park Mosque in north London, told the BBC.

"There's absolutely no reason given," said Khalid Oumar, the mosque's trustee. "We want to make sure HSBC is absolutely ashamed of what we believe is an Islamophobic campaign against Muslim organizations."

Until 2005 the mosque was headed by radical cleric Abu Hamza, who was convicted of terrorism-related charges in the U.S. this past May, but in the past ten years has made an intensive effort to improve its public image. The local MP Jeremy Corbyn said on Wednesday that it is a "superb example of a community mosque," and he is "appalled at the decision."

Anas Altikriti, chief executive of the Cordoba Foundation, believes the reason for the notice is not just Islamaphobia, but rooted in a direct political agenda.

"When you are left with no explanation, you are left to speculate," said Altikriti. "I would speculate that it is because of my activism either for Gaza or for the Palestinians. I have also been vocal in my attacks on the governments of Saudi Arabia and United Arab Emirates regarding their stand on the military coup in Egypt."

Altikriti says he has been met with nothing but a "wall of silence" in response to his requests for more information following the letter. Altikriti was born in Baghdad but moved to Britain as a child, where he says he opened an account as a teenager almost 30 years ago at a bank eventually bought by HSBC. Now he, his wife and their two sons—aged 12 and 16—were also notified that their personal accounts will be canceled, but were not given any reason whatsoever for those closures.

Muhammad Ahmad, trustee of the Ummah Welfare Trust, also believes the charity's support of Palestine to be the unstated cause of the termination notice. The UWT provides emergency relief such as food and medical supplies to victims in disaster areas, including Syria and Gaza. Ahmad said during Ramadan last week the charity received over £1 million in donations some days. Barclays also shut down the UWT's accounts during the attack on Gaza in 2008.

For its part, HSBC has said that the notices were "absolutely not based on the race or religion of a customer." An HSBC spokesman said the bank does not "discuss individual customers, nor do we confirm whether an individual or business is, or has been a customer," but that "for context" it was important to know that in 2012 the bank had to pay a $1.9 billion fine for facilitating transactions for customers operating money laundering and drug trafficking schemes in the U.S. The spokesman said that “the bank is applying a program of strategic assessments to all of its businesses."

But Nicholas Wilson, an HSBC whistleblower of alleged fraud, doesn't buy those claims.

"HSBC has a bank in Tel Aviv and have held a license there since 2001," he said. "They claim on their website to be the only foreign bank in Israel offering private banking. It could therefore be possible that they consider being seen to bank for pro-Palestinian organizations puts them in conflict with their ambitions in Israel."

Wilson said it's "a mixture of political pressure" and a belief on the bank's part that "assisting pro-Palestinian organizations would damage their reputation." He also noted that Sir Jonathan Evans, the ex-head of MI5, is now a non-executive director at HSBC.

The organizations are calling for a boycott of HSBC, and urging followers to use other institutions for their banking.