The Northern Airports Authority reported two incidents of burning straw in Soc Son District near the runway to the west of the airport on Sunday and Monday.

They created dense smoke, which hindered pilots' visibility during landing.

After receiving reports from air traffic control, aviation officials joined locals to put out the fires.

To guarantee the safety of flights at one of the country's busiest airports, the Northern Airports Authority urged the Hanoi city government to take urgent measures to stop people from burning straw in the airport’s vicinity and increase the frequency of patrols to deal with violators.

For long farmers on the outskirts of Hanoi have had the habit of burning straw after harvesting rice.

Last year the city had urged them to put an end to the practice by 2020.

Noi Bai, 45 km (28 miles) north of Hanoi center, is the country's second biggest airport after Tan Son Nhat in Ho Chi Minh City. A $5.5 billion expansion is planned to double its capacity to 50 million passengers per year by 2030.