Kenya's President Uhuru Kenyatta extended a nightly curfew on Monday for 30 days to curb the spread of Covid-19 and banned alcohol sales in restaurants but stopped short of locking down the country again despite a surge in cases.

The curfew had been due to be lifted on August 6 or 7.

Kenya has so far reported 17 975 cases of infection with the new coronavirus and 285 deaths from the related disease Covid-19. The health ministry said on Sunday it had reported 960 more cases, the biggest daily jump since the first case was confirmed in March.

"The harsh reality my friends is that we are at war. At war with an invisible enemy who is relentless," Kenyatta said in a televised address.

Kenyatta said the government had also shortened restaurant operating times by an hour, and ordered bars to stay closed indefinitely, but stopped short of reimposing a full lockdown.

"We cannot have a policeman at every street and in every village to enforce the rules. We need, as citizens, to hold ourselves and one another accountable," he said.

The outbreak has hit the economy, with the finance ministry projecting growth will slow to 2.5% this year from 5.4% last year.

Kenyatta said that among other measures, the health ministry would be authorised to convert government amenities such as schools and sports facilities into quarantine and isolation centres if needed.

He asked police to enforce the curfew rule regardless of who they found breaking it, without mentioning anyone by name.

Last week, the head of the senate committee overseeing the government's response to the coronavirus crisis quit his post after police said he flouted an overnight curfew to enjoy drinks with others in a Nairobi bar.

He was later charged and fined.

"All the measures ... shall be applied to all citizens regardless of their social or political standing," Kenyatta said.