Six people were killed in road accidents in Gaibandha and Tangail yesterday.

According to police, the accidents took place as dense fog reduced visibility on the highways.

Of them, four were killed as a bus and a CNG-run three-wheeler collided head-on in Gaibandha's Majhipara area around 5:30am, said Moshiur Rahman, station officer of fire service in Palashbari upazila.

Another man was injured in the accident, he added.

In Tangail, two people were killed and 15 others injured in three accidents.

In all the cases, vehicles crashed into one another from behind as dense fog made visibility poor on the Dhaka-Tangail highway, said Mollah Tutul, officer-in-charge of Gorai Highway Police Station.

A passenger bus, a truck and pick up were piled up in Dulla Mansur area around 9:00am, leaving an unidentified helper of the bus dead on the spot and inured few others, he said.

Meanwhile, an unidentified vehicle ran over a motorcycle in Baoikhola area around the same time, leaving the unidentified biker dead on the spot, the OC added.

The accidents occurred between 8:00am and 9:00am, he said.

The dense fag also disrupted flight schedules as four flights of different airlines were unable to land at Hazrat Shahjalal International Airport in Dhaka yesterday.

The flights were later diverted to Chattogram and India's Kolkata airports.

After being kept in a holding pattern for several hours, one flight was diverted to Chattogram airport and three others to Kolkata airport.

HSIA Executive Director Group Captain Kamrul Islam told The Daily Star that due to dense fog, the pilots were unable to see the runway.

An Abu Dhabi-Dhaka flight of Air Arabia and two flights of US-Bangla Airlines from Doha and Sharjah were diverted to Kolkata airport, while Fly Dubai's Dubai-Dhaka flight was diverted to Chattogram. All the flights landed safely.

Light to moderate fog was sweeping over most parts of the country for the last two days. It may continue till January, said AKM Nazmul Haque, meteorologist of the Bangladesh Met office.