Mr Johnston disappeared on 12 March and is feared kidnapped, though there has been no confirmed word on his whereabouts or his condition.
There has been a worldwide response to the online petition, which was opened on Monday, 2 April and coincided with a full page appeal in the UK's Guardian newspaper.
We have published 59,000 of the 69,000 signatures so far received and will publish regular further updates to the petition on this page.
The petition states:
"We, the undersigned, demand the immediate release of BBC Gaza correspondent Alan Johnston. We ask that everyone with influence on this situation increase their efforts to ensure that Alan is freed quickly and unharmed."
Se pretende assinar a petição pela libertação de Alan Johnston, visite a BBC Online.
Também pode colocar informação relativa a Alan Johnston, e um apelo à sua libertação, no seu blog ou página. Para isso, siga as instruções em www.bbc.co.uk.