Bobby Law, spokesman for the Rail, Maritime and Transport (RMT) union told Sky news: "Hundreds yesterday [Thursday] were saying they were going to refuse work should a situation arise like it did yesterday."
Yesterday's newspapers focused on the "miraculous" escape by hundreds of commuters after the devices only partially detonated without causing any injuries.
Explosives experts said it was still unclear why the devices had failed to explode properly.
Meanwhile, Muslim leaders expressed concern at the shooting.
Inayat Bunglawala, a spokesman for the Muslim Council of Britain, said he had spoken to ``jumpy and nervous'' Muslims after the shooting. "I have just had one phone call saying `What if I was carrying a rucksack?' It's vital the police give a statement about what occurred and explain why the man was shot dead."
RSS