Britain Arrests 6 in Counterterrorism Raids

LONDON — The British counterterrorism police arrested six people on Tuesday in raids across southern England following other detentions in London and the English Midlands.

The detention of three men and three women in Portsmouth and Farnborough, both in Hampshire, and in Greenwich, in southeast London, reflected heightened concerns that the rise of the Islamic State, also known as ISIS or ISIL, has helped foment jihadism, particularly among young Muslims.

The arrests came a day after three men were detained in central London, part of a series of detentions since Britain raised its terrorism threat assessment to “severe” — its second-highest level — in August.