Iran has severed internet access nationwide for more than 12 hours, an independent tracker says, after Tehran authorities instituted restrictions aiming to thwart alleged Israeli military cyber offensives.

The government cited the recent hacks on Bank Sepah and cryptocurrency exchange Nobitex as reasons to shut down internet access to virtually all Iranians.

Iranians managed to gain some unreliable connection to the internet on Friday after a near-total blackout that lasted four days.