Saudi Arabia has postponed the public lashing of a liberal blogger on medical grounds, according to Amnesty International, as the UN joined a chorus of international leaders calling for him to be pardoned.

Amnesty said on Friday that Raif Badawi was taken for a medical check-up before his sentence of 50 lashes was due to be carried out.

Breaking news: Flogging of Raif Badawi has been postponed on medical grounds. More details soon. #FreeRaif — AmnestyInternational (@AmnestyOnline) January 16, 2015

The rights group said a doctor at a prison clinic treating the activist said his wounds had yet to heal from his first round of flogging and he would not be able to withstand another round of lashes at this time.

"The notion that Raif Badawi must be allowed to heal so that he can suffer this cruel punishment again and again is macabre and outrageous," Said Boumedouha, Amnesty International’s Deputy Director for the Middle East and North Africa Programme.

"Flogging should not be carried out under any circumstances," he added.

Badawi, who started the "Free Saudi Liberals" website, was sentenced to 10 years in prison and 1,000 lashes on charges related to accusations he insulted Islam on the online forum.

He is due to undergo 50 lashes every week after Friday prayers, which will continue for 20 weeks until his punishment is complete.

On Thursday, the UN human rights chief, Zeid Ra'ad Al Hussein, joined the US, Amnesty and Reporters Without Borders in calling on Saudi's King Abdullah to cancel the sentence.

"Flogging is, in my view, at the very least, a form of cruel and inhuman punishment," Hussein said in a statement.

He appealed to King Abdullah "to halt the public flogging by pardoning Badawi, and to urgently review this type of extraordinarily harsh penalty".

Around 14,000 people have so far signed an online petition calling on Saudi's King Abdullah to pardon Badawi.