The UK says Iran is "almost certainly" responsible for attacks on two oil tankers in the Gulf of Oman.
The US president's comments come after five separate attacks in London leave three men dead.
People are warned they may need to stay out of their homes in Lincolnshire for up to 48 hours.
Former contender Esther McVey pledges support to Boris Johnson ahead of the first TV debate later.
Fodor's Travel compared "wildly romantic Catholic murals" to "workmanlike efforts" in Protestant areas.