A Syrian government offensive on the rebel-held eastern part of the city has entered its fourth day, after diplomatic efforts broke down last week.

Residents say the ferocity of the bombing is "unprecedented".

They shelter in their basements -- but the onslaught includes bunker-busting bombs that bring down entire buildings with people huddled inside.

A quarter of a million people are trapped in eastern Aleppo.

Hundred have been reported killed in the bombing including dozens of children.

The offensive has backing from Syria's allies -- Russian war planes in the skies and Iranian support on the ground.

The latest escalation has left Syria diplomacy in tatters.

It's all but destroyed hope of a breakthrough this year.

In Aleppo's rebel-held east, one city leader says the "future" is unclear.

"It looks like there's more killing", he says. "More bombardment, more blood on the horizon".

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.