Strikes by Southern Railway workers on Thursday and Friday have been called off but services will still be disrupted even though fresh talks are to be held in the bitter row over the role of conductors.

Members of the Rail, Maritime and Transport (RMT) union walked out on Monday and were due to stay out until the weekend, causing travel chaos for hundreds of thousands of passengers.

Following an offer from the RMT to suspend the action if Southern returned to talks without any preconditions, Acas announced that new talks will be held on Thursday.

But Southern, part of the giant Govia Thameslink Railway franchise, said Thursday's service will be based on the present strike timetable, although it will try to add services.

And the RMT is pressing ahead with four days of strike action from Friday on Eurostar in a separate row over the work/life balance of train managers.

Eurostar has cancelled a London to Brussels train and a Brussels to London service on Friday but expects to run a normal service on Saturday.

Further strikes are planned over the August Bank Holiday weekend by the RMT, and the TSSA union.

RMT general secretary Mick Cash said he had contacted Southern with a way forward to resolve the dispute.

"Please be advised that I have now received communication from the conciliation service Acas informing me that the company will now enter into negotiations with our union officials without any preconditions," he said.

"You and your colleagues are therefore instructed to return to work for all shifts commencing from 22.00hrs tonight."

A Southern spokesman said: "We are encouraged that the RMT has accepted our offer to resume talks at Acas and has agreed to call off its strike action.

"For our passengers' sake we truly hope these talks will be productive and bring this long-running dispute to an end.

"At present, the strike timetable is still in the industry train planning systems for Thursday and Friday. Regrettably, this means tomorrow's service will be based upon the present strike timetable, but we will do our very best to add services in and extend the hours of operation wherever possible.

"On Friday we plan to revert to the revised timetable operating before the strike. We will update our website www.southernrailway.com as further information becomes available."

Transport Secretary Chris Grayling said: "This is good news for passengers. This strike has inconvenienced people needlessly and I am glad to see RMT sitting round the table as I called for yesterday.

"It's important now to leave the union and the train operator to undertake these necessary talks. I hope they reach a positive conclusion as quickly as possible."

On the Eurostar dispute, Mr Cash said: "Our train manager members at Eurostar have a heavy commitment to shift work and unsocial hours and are sick and tired of the company's failure to honour agreements.

"Our members have every right to have a fair work/life balance that fulfils the operational needs of the company while guaranteeing quality time off for friends and family."

A Eurostar spokesman said: "We are aware of the plans for strike action and our focus has been seeking a joint resolution whilst planning to provide a good service for our customers.

"On the days of the strike we have made some small changes to our timetable to ensure that all passengers booked to travel will be able to on those days. Passengers affected will be notified in advance."