Dairy farmers have vowed to continue protests outside milk processing plants unless their demands for "fair" milk prices are met.
Campaign group Farmers for Action (FFA) said about 750 of its members turned out to demonstrate outside the Robert Wiseman dairy in Droitwich Spa, Worcestershire, and another plant at Foston, Derbyshire.
The protests took place hours after a move by the Co-operative Group to increase the premium it pays to its farmers for their milk to 29p per litre.
Farmers for Action welcomed the retailer's announcement - which also received a positive response from the National Farmers Union - as a step forward.
But FFA's vice chairman Andrew Hemming, who farms near Hockley Heath, West Midlands, said further protests would be held unless there was movement from further milk retailers and processors.
The protest group, which has warned that milk price cuts will force hundreds of farmers out of business, has also threatened to disrupt milk supplies if the issue is not resolved by the end of the month.
Mr Hemming, who was among almost 250 people who protested in Droitwich until midnight, said: "It's hard work - it's annoying that we have to go to these lengths to make common sense prevail.
"We had a fantastic turn-out at Foston - towards the end there were nearly 500 farmers up there and they blockaded until 3am."
FFA, which is not planning to stage any further protests until Sunday, is also lobbying outside supermarkets to get its message across to consumers.
Thanking consumers for backing the FFA campaign through Facebook and Twitter, Mr Hemming said it had proved an effective way for the public to pressure retailers and processors into acting fairly.