Bangladeshi opposition parties are preparing to launch a 48-hour strike against a government they accuse of clinging to power and undermining democracy.

The main opposition Bangladesh Nationalist Party and its allies including the Islamist group Jamaat-e-Islami say the strike will begin Wednesday morning at 6 a.m. local time. The parties have been protesting last month's parliamentary approval of a constitutional amendment that scraps a system of holding national elections under non-partisan caretaker governments.

Lawmakers from the ruling Awami League of Prime Minister Sheikh Hasina passed the amendment in a June 30 vote boycotted by the BNP. Bangladesh's Supreme Court issued a ruling in May saying the system of installing 90-day interim administrations to supervise elections is unconstitutional.

Critics of the system said the last caretaker government that took office in January 2007 exceeded its mandate by holding onto power with military backing for two years until holding elections in December 2008. Ms. Hasina won that vote, defeating BNP leader Khaleda Zia, her longtime rival and predecessor.

Ms. Zia's BNP and other opposition parties accuse Ms. Hasina of amending to constitution to keep the Awami League in power through fraud, rather than allowing non-partisan technocrats to oversee Bangladesh's next elections.

Authorities in the capital, Dhaka, say suspected opposition activists set fire to five buses and a van on Tuesday as part of a protest campaign leading up to the two-day strike. But, Bangladeshi news agency bdnews24.com quoted a BNP official as saying the government was behind the vandalism.