At least a dozen people were injured after several vehicles crashed and created a pile-up on the busy Lucknow-Agra Expressway in Unnao on Tuesday after dense fog enveloped the state.

According to police, the shocking mishap was a result of low visibility.

"Pile-up of around a dozen vehicles took place early this morning on the Agra-Lucknow Expressway in Jogikot village under Bangarmau police station," said Additional Superintendent of Police Ambrish Bhadauria was quoted as saying by PTI.

Fortunately, the victims sustained minor injuries.

"The injured persons were administered first aid at the community health centre in Bangarmau, and were subsequently sent home," Bhadauria added.

The pile-up comes a few days after a similar accident caused by the crashing of 18 speeding vehicles on the Agra-Noida Yamuna Expressway killed at least one and left six others injured.

Meanwhile, the fog is affecting several areas in the North and has taken a toll on the train services a lot.

According to an India Today report, at least 18 trains were cancelled, 28 were delayed and three were rescheduled due to fog. The dense fog has also given rise to a cold wave in UP.

Here are a few visuals of a few regions in UP.