Summary:
British police say they have arrested four men in connection with a terror plot in London.

Full article:
(CNN) -- A fifth man has been arrested on suspicion of planning an act of terrorism, British police said Thursday. All the men, ages 20 and 21, remain in custody at central London police stations. The warrant for further detention has been granted until October 14, police said. The arrests come nearly two weeks after police arrested at least 10 other men in the United Kingdom on suspicion of terror offenses, including supporting a banned organization and encouraging terrorism. A UK security source said Tuesday that authorities may have foiled a terror plot aimed at Britain in its early stages. Islamic terrorism was "the clear reason" for the plot, according to the source. After four men were arrested earlier this week, Scotland Yard said they are being held on suspicion related to the "commission, preparation or instigation of act of terrorism." Authorities have not detailed exactly where or when such terrorist attacks might have occurred or what or who they might have involved. Metropolitan Police Commissioner Bernard Hogan-Howe, in an interview with BBC local radio, said many recent arrests are "linked back to Syria and Iraq." In the latest arrests, authorities said they searched residences and vehicles in west and central London as part of the investigation. UK police arrest 4 men suspected of terror plot . CNN's Alex Felton in London contributed to this report.