Two Christian families have been denied entry to the United States and sent home.

They were among the first casualties of President Donald Trump's travel ban on people from seven Muslim-majority countries.

Two brothers, their wives and two children from Syria were turned away from Philadelphia International Airport in the United States and sent back, according to a source in Beirut.

Trump signed the controversial executive order on Friday banning people from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen from entering the United States. All refugees are also banned for 120 days and refugees from Syria are banned indefinitely.

Trump said the ban was "not about religion". He said in a statement: "To be clear, this is not a Muslim ban, as the media is falsely reporting. This is not about religion – this is about terror and keeping our country safe. There are over 40 different countries worldwide that are majority Muslim that are not affected by this order. We will again be issuing visas to all countries once we are sure we have reviewed and implemented the most secure policies over the next 90 days."

But there are fears the ban could act as a recruiting tool for Islamic State. 

Besides prohibiting travel from seven Muslim-majority countries, the ban prohibits entry to all refugees, regardless of origin, for 120 days and indefinitely for refugees from Syria, which has been ravaged by a deadly war since 2011. After the 120 day period is over, priority will be given to Christian refugees, Trump told the Christian Broadcast Network.

Of more than 3,000 people who entered the US yesterday, more than 100 were detained for questioning.

After the British Government became so concerned it contacted the White House, Foreign Secretary Boris Johnson was reassured by Trump advisers that British nationals with dual citizenship will not be banned from entering the US, at least not if they are travelling from Britain.

The ban only affects people travelling directly from those seven countries to the US.

However, the two Christian families from Syria were returned to the Middle East from Philadelphia in spite of reassurances from Trump that the executive order would give priority to admitting Christian refugees.

A source told AFP. "Six people, including Syrian Christians, were turned back at Philadelphia airport on Saturday and were back in Beirut on Sunday."

Just hours before they were sent back, Trump had told the Christian Broadcasting Network, referring to Christian refugees in general: "We are going to help them. They've been horribly treated."