The New York Post has apologised after its app was apparently hacked on April Fools' Day, sending out a series of unusual push alert notifications including one reading "Heil President Donald Trump".

"The push alert system for our mobile app was compromised this evening," The Post tweeted.

"Please accept our apologies."

Post subscribers seemed confused, taking screenshots of the alerts and sharing them on social media.

Some of the messages included religious references.

"Hear me now, for I speak as an angel in the words of God," the hacker wrote.

"In casting truth into the darkness of your shadow, you have gravely sinned."

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One alert read "take your time, hurry up, the choice is yours, but don't be late" — lyrics from Nirvana's Come As You Are.

The sender signed off "with Lucid Love, Selah".

Selah is word which appears in Psalms in the Hebrew Bible. Its meaning is unknown.

Earlier this month, fast food giant McDonald's said its Twitter account was hacked after its corporate account posted a tweet critical of Mr Trump.

In the aftermath, #BoycottMcDonalds began trending.

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ABC and wires