Workers who say they've been unpaid for months by Nigeria's biggest airline went on strike Tuesday, halting flights and stranding thousands of passengers days before Christmas.

Arik Air operations stopped before dawn, Ahmed Roland Maikudi, vice president of the National Association of Aircraft Pilots and Engineers, told The Associated Press. He said pilots and other workers have not been paid for up to five months.

"We Say No To Slavery!" said placards waved by chanting workers who picketed the airline's padlocked headquarters at Murtala Muhammed International Airport in Lagos, Nigeria's commercial hub. Strikers blocked the entry with vehicles.

Arik Air said strikers have blocked officials from entering the domestic and international terminals.

Arik, which flies more than 100 domestic and international flights daily, accused labor organizations of using "strong-arm tactics" trying to unionize its work force.

Arik spokesman Ola Adebanji said reports that workers have not been paid for seven months are "not true." But he did not respond to the charges that workers have not been paid for between two and five months.

The airline has been struggling for weeks with delayed and cancelled flights usually blamed on aviation fuel shortages. A Dec. 17 statement says the airline has been able to procure only about 200,000 of the 500,000 liters of fuel needed daily.

Two other Nigerian airlines suspended operations weeks ago, and two international carriers recently stopped flying to the country. Africa's largest economy, and the continent's second-biggest oil producer, is struggling in a recession caused by low oil prices and a massive shortage of foreign currency.

Other international airlines have taken to refueling in neighboring Ghana, losing Nigeria its spot as the leading airline hub in West Africa.

AP