Hundreds of workers at Kenya's main international airport demonstrated on Wednesday against a planned deal between the government and a foreign investor. Planes have remained grounded, with hundreds of passengers stranded at the airport.

The government has said that the build-and-operate agreement with India's Adani Group would see the Jomo Kenyatta International Airport modernized, and an additional runway and terminal constructed, in exchange for the group running the airport for 30 years.

Kenya Airport Workers Union, in announcing the strike, said that the deal would lead to job losses and "inferior terms and conditions of service" for those who will remain.

Kenya Airways on Wednesday announced there would be flight delays and possible cancellations because of the ongoing strike at the airport, which serves Nairobi.

The strike has affected local flights coming from the port city of Mombasa and the lake city of Kisumu, where delays have been reported by local media.

At the main airport, police officers had taken up security check-in roles with long lines seen outside the departure terminals and worried passengers unable to confirm if their flights would depart as scheduled.

The Kenya Airports Authority said in a statement that it was "engaging relevant parties to normalize operations" and urged passengers to contact respective airlines to confirm flight status.

The Central Organization of Trade Unions' secretary-general, Francis Atwoli, told journalists at the airport that the strike would have been averted had the government listened to the workers.

"This was a very simple matter where the assurance to workers in writing that our members will not lose jobs and their jobs will remain protected by the government and as is required by law and that assurance alone, we wouldn't have been here," he said.

Last week, airport workers had threatened to go on strike, but the plans were called off pending discussions with the government.

The spotting of unknown people moving around with airport officials taking notes and photographs raised concerns that the Indian firm officials were readying for the deal, local media outlets reported last week.

The High Court on Monday temporarily halted the implementation of the deal until a case filed by the Law Society and the Kenya Human Rights Commission is heard.