The number of deaths from coronavirus in Iran is nearly triple what Iran's government claims, a BBC Persian service investigation has found.

The government's own records appear to show almost 42,000 people died with Covid-19 symptoms up to 20 July, versus 14,405 reported by its health ministry.

The number of people known to be infected is also almost double official figures: 451,024 as opposed to 278,827.

The official numbers still make Iran the worst-hit in the Middle East.

In recent weeks, it has suffered a second steep rise in the number of cases.

The first death in Iran from Covid-19 was recorded on 22 January, according to lists and medical records that have been passed to the BBC. This was almost a month before the first official case of coronavirus was reported there.

Since the outbreak of the virus in Iran, many observers have doubted the official numbers.

There have been irregularities in data between national and regional levels, which some local authorities have spoken out about, and statisticians have tried to give alternative estimates..

A level of undercounting, largely due to testing capacity, is seen across the world, but the information leaked to the BBC reveals Iranian authorities have reported significantly lower daily numbers despite having a record of all deaths - suggesting they were deliberately suppressed.