A further section of the Brecon Beacons national park has been put into lockdown, meaning people will not be allowed to enter or leave the area without a reasonable excuse.
The movement restrictions in the Merthyr Tydfil county borough came into force at 6pm on Tuesday.
The out-of-bounds area include the village of Pontsticill, the south-western part of Pontsticill Reservoir and a section of the Brecon Mountain Railway.
The newly restricted region lies immediately to the East of Rhondda Cynon Taf, which was put into local lockdown on Thursday.
The Welsh Government imposed local restrictions on Merthyr Tydfil, along with Bridgend, in response to rising coronavirus cases in the areas.
Visitors may not enter the restricted areas without reasonable excuse, and residents of the affected areas can only travel for exercise and cycle within the county borough area. People from outside the area can drive through it on their way to their destination if there is no practical alternative.
The government said it will review the rules in two weeks and each week following that if they are still in force.
Residents of each affected area are not allowed to travel to the other locked-down boroughs.
South Wales Police said it will continue to support Welsh Government and local partners to implement the restrictions, adopting the same 4Es approach – engage, explain, encourage and enforce – used since the beginning of the pandemic.
A force spokesperson said: “Our officers will be visible in our communities, working with the public to engage, explain and encourage compliance. Enforcement action will be taken where necessary and proportionate.”
A fixed penalty notice can be issued for most types of breaches of the regulations, carrying a fine of £60. This is increased to £120 for a second offence and continues to double for repeated offences, up to a maximum of £1,920. If prosecuted a court can impose an unlimited fine.