Prime Minister Tusk has visited the site of an explosion that damaged a railway line leading to the Ukrainian border. He said the damage was deliberate and expressed relief that there were no casualties. Tusk also vowed to catch those responsible, "regardless of who their backers are". Poland's special services minister Tomasz Siemoniak said there was a "very high chance" that the blast was carried out on the orders of "foreign services". He didn't name Russia directly, but Poland "has experienced a series of major arson and sabotage attacks in recent years, including parcel bombings, that it sees as part of Moscow's hybrid war on the West", writes Sarah Rainsford. Russia always denies any role in such attacks.