A failed slurry lagoon has caused "major pollution" in Monmouthshire.

Natural Resources Wales (NRW) said the incident, near Abergavenny, is likely to have a "serious effect" on some rivers in south east Wales.

A "significant discharge" from the lagoon, which contained up to 450,000 litres (99,000 gallons) of slurry, went into a tributary of the River Honddu.

NRW officers are also assessing the impact on the River Monnow and River Wye.

Caroline Drayton, a team leader for NRW, said on Tuesday: "Protecting nature in Wales is our biggest priority and we have been carrying out pollution-prevention works to minimise the impact of this incident since this morning."

NRW is working closely with the Environment Agency in England to monitor the situation.