A 33-year-old and a 42-year-old were arrested on the M6 motorway near Rugby in Warwickshire as part of a probe into Islamist-related terrorism and are now being questioned at a police station in London.
The nine others, including radical Islamist preacher Anjem Choudary, remain in custody after being arrested yesterday.
The 33-year-old has been arrested for "encouraging terrorism" and "being a member of a proscribed organisation", the Metropolitan Police's Counter Terrorism Command said in a statement.
The police stressed that the arrests were part of an ongoing inquiry into Islamist-related terrorism and not in response to any immediate threat to the public.
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The police had arrested Choudary, one of the most high-profile Islamists in the UK, as part of the same investigation into alleged encouragement of terrorism.
Choudary, 47, was a former spokesperson for the banned extremist or radical group al-Muhajiroun, which the government says reinvented itself under various names, which were also proscribed.
He has denied all allegations, saying that he has neither incited nor glorified acts of terrorism.
The UK last month raised its international threat level to the second-highest level of "severe", meaning an attack is considered highly likely, while Prime Minister David Cameron has said the Islamic State militant group in Syria and Iraq poses the country's greatest ever security risk.