Plainclothesmen initially arrested Bangladesh Nationalist Party's (BNP) three highest policymaking standing committee members - Moudud Ahmed, MK Anwar and Rafiqul Islam Mia.
The three leaders were arrested overnight while returning to home after attending the anniversary celebration of a newspaper here. Mintoo and Biswas were whisked away from outside Zia's Gulshan residence at around 1 am (local time).
Later, they detained Zia's adviser and business tycoon Abdul Awal Mintu and her special assistant Shimul Biswas.
Angry opposition activists took to the streets, setting several vehicles on fire and exploding bombs. Police also carried out midnight raids at the houses of several other influential BNP leaders who went underground to evade arrests.
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"We were forced to take the tougher stand in an extra-ordinary situation to protect the nation from acts of anarchy," Information Minister Hassanul Haq Inu told newsmen in brief comments last night.
Inu did not elaborate on the anarchy, but according to reports the opposition leaders in a close door meeting with Zia last night planned to go ahead with a nationwide strike on November 10, 11 and 12 to mount pressure on government.
The BNP-led alliance called the first 60-hour shutdown from October 27 and second one from November 4 to press for the restoration of the caretaker government.
In a hurriedly called press conference here, BNP's joint secretary general Ruhul Kabir Rizvi blasted the government for the "crackdown" and termed the arrests as manifestation of the government aggression on opposition.
"But tougher action will await the government unless our leaders are freed immediately," he said.
Premier Sheikh Hasina and her arch-rival Zia are the most powerful leaders in Bangladesh and they have alternated as prime minister since 1991.