LONDON (Reuters) - An earthquake with a preliminary 6.6 magnitude struck 256 miles east of the Solomon Islands on Thursday, the U.S. Geological Survey said, the latest aftershock following a tremor that caused a tsunami which killed at least five people. The quake was 6.2 miles deep and located southeast of Kira Kira. There was no immediate tsunami warning. (Editing by Angus MacSwan)