Maintenance contract workers at ConocoPhillips' (COP) 221,000 barrel a day Humber refinery in northern England walked out for a second day Wednesday, the company said.

"The action is unrelated to ConocoPhillips local employment practices...the action has not affected the normal operations at the site and we look forward to the situation being resolved as soon as possible," the company said in an e-mailed statement.

The Humber contractors held an unofficial strike for a second day in sympathy with workers from the South Hook liquefied natural gas terminal at Milford Haven, Wales. They were joined by contractors at Total SA's (TOT) nearby Lindsey oil refinery, which has a capacity of 200,000 barrels a day.

The South Hook contractors went on strike Tuesday to protest the hiring practices of industrial services company Hertel U.K. for an insulation project, which they said was unfair to local workers.

Workers at the Dragon LNG import terminal in Milford Haven and RWE AG's (RWE.XE) Aberthaw Power Station in Wales also walked out on Tuesday, but it wasn't clear if they had continued the strikes Wednesday.

-By Lananh Nguyen, Dow Jones Newswires; +44 (0)20-7842-9479; lananh.nguyen@dowjones.com