A Bangladeshi court Monday ordered an investigation into an allegation of murder against opposition leader Khaleda Zia over the death of dozens of people in petrol bomb attacks during a continuing transport blockade.

The order from a lower court in the capital Dhaka comes after a pro-government activist, A. B. Siddiqi, filed a private complaint against Zia, the leader of the main opposition Bangladesh Nationalist Party (BNP).

The owner of a leading Bangladeshi television station has been arrested as part of a wider crackdown on the opposition in a deepening political crisis that has left nearly 50 people dead, police said Monday.

Several networks broadcast footage of a police officer getting into the car of Mosaddek Ali Falu, chairman of private station Ntv, after he came out of the office of opposition leader Khaleda Zia on Sunday night.

At least 13 people were killed and more than a dozen injured on Saturday when a fire broke out in a plastic factory in Bangladesh's capital, emergency service officials said. 

Police and fire officers believe the blaze started when gas cylinders exploded in the factory's boiler room, then raced through the four-story Nasim Plastic factory in minutes.

Dozens of people are missing after an overloaded fishing trawler carrying migrants to Malaysia sank in strong currents off the coast of Bangladesh on Thursday, officials said.

Emergency workers rescued 43 Bangladeshis in the Bay of Bengal after the boat capsized some 2.5 kilometers (1.5 miles) offshore, police and the coastguard said.

Tens of thousands of mourners turned out Tuesday for the funeral of Bangladesh opposition leader Khaleda Zia's son in a massive show of support for the embattled former premier.

Arafat Rahman Koko, 44, died of a heart attack on Saturday in Malaysia, a devastating blow to the opposition leader after she launched fresh protests this month to try to topple bitter rival Prime Minister Sheikh Hasina.

Bangladesh security forces have arrested more than 7,000 opposition activists since the start of deadly protests a fortnight ago, the government said.

Activists have firebombed buses, cars and lorries, killing 29 people, since the opposition called a nationwide transport blockade to protest the detention of their leader Khaleda Zia.

Bangladesh police said Monday they have arrested four suspected members of the Islamic State jihadist group including a "local coordinator" who was planning to establish a self-declared "caliphate" in the country.

The suspected coordinator Mohammad Sakhawatul Kabir and three others were detained in the capital following raids on Sunday, Dhaka Metropolitan Police said in a statement.

Four killed as bus firebombed in Bangladesh unrestA firebomb attack on a bus killed four people Wednesday, including a young child, while an aide to opposition leader Khaleda Zia survived an assassination attempt in a new upsurge of political unrest in Bangladesh.

The attack on the bus in the northern town of Mithapukur was carried out as anti-government activists tried to enforce a transport blockade as part of efforts to force the downfall of Prime Minister Sheikh Hasina.

Bangladeshi police shot and killed two people overnight during ongoing violent opposition protests against the first anniversary of Prime Minister Sheikh Hasina's controversial reelection, a senior officer said Thursday.

More than 5,000 supporters of besieged opposition leader Khaleda Zia attacked police with sticks in southern Noakhali district late Wednesday, forcing them to "open fire in self defense," the officer said.

Bangladesh authorities Tuesday threatened to bring murder charges against besieged opposition leader Khaleda Zia and arrested her deputy over accusations that they incited a nationwide wave of deadly violence.

A day after Prime Minister Sheikh Hasina accused Zia of trying to trigger anarchy, a minister said her arch rival should expect a murder charge over an arson attack which left three people fighting for their lives.