UK PM candidate Johnson says sorry for any offence his words have caused

Boris Johnson, the frontrunner to be Britain's next prime minister, apologised on Tuesday for any offence caused over his earlier comments, including those when he described Muslim women wearing burqas as looking like letter boxes.

"In so far as my words have given offence over the last 20 or 30 years when I've been a journalist and people have taken those words out of my articles and escalated them, of course I am sorry for the offence they have caused," he said in a televised debate.