Kuwaiti exports and imports were disrupted Monday as over 3,000 customs officers went on strike demanding better pay and threatening to halt oil exports, a trade union official said.

"The strike is total as all of the more than 3,000 customs employees have stopped work. We are on an indefinite strike until our demands are met," Fahhad al-Ajmi, board member of the customs trade union, told AFP.

Work at the country's only airport was "partially affected" but there was a "complete halt to shipping and land freight," Ajmi said.

He warned that oil exports from Kuwait, OPEC's third largest producer "could be affected later in the day" if the strike continued as all tankers carrying crude must receive clearance from customs to leave.

Ajmi said that at least one oil tanker on Monday was barred from sailing because it was not given the necessary customs clearance.

State-owned Kuwait Petroleum Corp (KPC) could not immediately be reached for comment.

Customs employees are demanding a pay raise and improved work conditions, Ajmi said, adding that workers have already rejected an offer by the customs chief, Ibrahim al-Ghanem, to meet their demands if they called off the strike.

Kuwait has been hit by a spate of industrial action in the public sector, which employes close to 80 percent of the 360,000-strong workforce of Kuwaiti nationals.

The country has about 1.7 million foreign workers, mostly employed by the private sector.

The industrial actions escalated last month after the government increased the salaries of oil workers at a cost of more than $500 million a year, bowing to strike threats in the key revenue earning sector.

Finance Minister Mustafa al-Shamali has said that the public sector wage bill has more than doubled over the past decade.

Government spending has tripled since 2005 to a record $71 billion, with public sector salaries estimated to account for at least a third of total expenditures.

The Gulf state, which counts 1.2 million Kuwaiti nationals, offers a cradle-to-grave welfare system with public services and fuel offered either free or at heavily subsidised prices, and no taxes.