An anti-government strike shut down much of Bangladesh Wednesday, as opposition members protested a constitutional amendment they say will allow the ruling party to cling to power.

Schools and businesses were closed throughout the country, and operations at Bangladesh's main port in Chittagong were suspended.

At least 20 people were injured Wednesday as security personnel and demonstrators clashed in several parts of the country. A senior leader of the main opposition Bangladesh Nationalist Party, Zainal Abdin Farooque, was hospitalized with head injuries in the capital, Dhaka. Several BNP members were also arrested during the clashes.

Home Minister Sahara Khatun has warned the government will do whatever is necessary to maintain order.

The BNP and its allies, including the Islamist group Jamaat-e-Islami, began the two-day strike Wednesday to protest last month's parliamentary approval of a constitutional amendment that scraps a system of holding national elections under a non-partisan caretaker government.

Lawmakers from Prime Minister Sheikh Hasina's ruling Awami League party passed the amendment in a June 30 vote boycotted by the BNP.

Opposition members accuse Ms. Hasina of amending the constitution to keep her party in power through fraud, rather than allowing non-partisan technocrats to oversee Bangladesh's next elections.

The country's supreme court has ruled the system of installing 90-day interim administrators to supervise elections is unconstitutional.