About 500 barrels of oil has leaked from a pipe off the north Wales coast. The pipe, which runs between two platforms named Conwy and Douglas, was shut off following the leak on Monday and remains closed.

Operator ENI UK said details of what happened about 20 miles (33km) north of Rhyl, Denbighshire, were still being confirmed, but no-one was affected. The firm said there would be updates as details emerged but the Welsh secretary said no oil should reach Wales’ shores.

A leak of about 500 barrels is just under 80,000 litres.

The Douglas complex consists of three platforms and is located about 15 miles (24km) off the north Wales coast. The Maritime and Coastguard Agency said its counter pollution and salvage team, together with the Department for Business, Energy and Industrial Strategy, was monitoring ENI’s response and was “assisting partner local authorities in an ongoing response”.

News of the spill came on the 26th anniversary of what has been called Wales’ worst ecological disaster, when 72,000 tonnes of crude spilled from the Sea Empress oil tanker off the Pembrokeshire coast. Large numbers of seaweeds and invertebrates were killed on the beaches where it drifted ashore, and it took over a year to clean the slick.

The Conwy to Douglas pipeline ‘was shut immediately’ after the hydrocarbon release, reported on last Monday,  and the north Wales coast is being monitored.

Reports from later in the week stated that “tar balls” have begun washing up on beaches in the North West of England. Balls of congealed tar from the spill have been spotted along the coastline on Blackpool as tidal conditions and extreme weather conditions push the spill inland.