Some flights and Eurostar services to and from the UK are suffering delays and cancellations owing to a day of anti-austerity protests across Europe. Eurostar said London-Brussels services could be disrupted throughout the day, and advised against non-urgent travel. British Airways has cancelled 10 return services between London and cities in Spain and Portugal, while Easy jet has cancelled more than 20 European trips. General strikes in Spain and Portugal halted transport, closed businesses and schools and led to clashes between police and protesters in Madrid. Smaller strikes were reported in Greece, Italy and Belgium, as the Europe-wide day of action was due to involve 23 countries. Some 39 flights - nearly all involving Spain or Portugal - were cancelled at London Heathrow Airport. "Most people seem to have got the message that some flights were going to be axed and the terminals are operating smoothly," an airport spokeswoman said. "Flight cancellations are never good news, but we do operate around 1,300 flights a day so the figure of 39 is a comparatively small one." After cancelling its 10:57 GMT London to Brussels service, Eurostar said it was hoping to accommodate affected passengers on the 12:57 service. Customers can exchange their tickets for Wednesday to another day and time, the company said. Services between and London and Paris are running normally. There were delays to some Easy jet flights, including a London-to-Greece service that departed three hours and 40 minutes late. The airline said: "We are proactively trying to minimise disruption. However, we would like to warn customers that they could experience delays to their travel plans." British Airways said customers on Spain flights on Wednesday could re-book free of charge, while there would be full refunds for cancellations. "We are also looking at putting on larger aircraft to help as many customers as possible," the airline added. Unions in Spain and Portugal started strikes at midnight to protest against austerity measures that have combined tax rises with cuts in salaries, pensions, benefits and social services. The protests have led to outbreaks of violence in several Spanish cities. In Greece, the strike action is the third major walkout in two months.