* Port is main trade gateway to east African region
* 3,500 workers down tools to demand permanent jobs
* Loading and unloading of ships halted by strike (Adds details)
By Joseph Akwiri
MOMBASA, Kenya, Nov 1 (Reuters) - An indefinite strike by more than half of the workers at Kenya's main port of Mombasa on Thursday has paralysed dockside work at east African region's main trade gateway, union and management officials said.
The port, the biggest in the region, handles imports such as fuel for Uganda, Burundi, Rwanda, South Sudan, eastern Democratic Republic of Congo and Somalia.
The union said 3,500 workers, most of whom are loaders, and had worked at the port for between 15 and 20 years on casual and contractual basis, went on strike demanding permanent jobs.
"The most affected area is the operations section which deals with cranes and ships, and that is our core area," said Bernard Osero, the port corporate affairs manager.
The port employs about 6,000 workers in Mombasa, he said.
The workers, in aprons and reflective jackets, camped outside the port head offices in Mombasa, chanting slogans and waved banners, while import-loaded cargo ships waited.
Simon Sang, secretary general of the dock workers union said the management had agreed earlier this year to employ the casual workers by October 31 but this had not yet happened, prompting the industrial action.
The union leaders and port management said loading and unloading at the port were at a total standstill.
"We don't want any more meetings and negotiations because we already did that, what we want are the (employment) letters, otherwise we will not go back to work," Sang told reporters.
Kenya Ports Authority (KPA) Managing Director Gichiri Ndua arrived from a trip to the capital Nairobi and went straight into a meeting with leaders of the striking workers.
The port handled 10.7 million tonnes of cargo over the first-half of this year, up 24 percent from 2011. The traffic is usually an indicator of economic activity in the region.
The port of Mombasa serves its wide hinterland with imports that include oil, clinker which is used to make cement, steel, bitumen for road construction and second-hand cars, while the main exports include tea, coffee, and horticulture goods.
"We had carried 1,283 units of vehicles to be discharged here at Mombasa, we only discharged 800, and had to stop because of the strike," said Richard Bataanon, a Philippines national and seaman in charge of MV Delphinus Leader, which had originated from Japan with its cargo of vehicles
"We can't discharge the 400 remaining and this is eating up our time because we are heading to Durban in South Africa. We will wait until we are able to discharge before we proceed with our journey," he said.
"We hope the port will not charge us demurrage fees because this is not our fault."
Labour unrest has become more frequent across east Africa's biggest economy this year ahead of presidential and parliamentary elections due next March.
Teachers, university lecturers and doctors have also staged strikes to demand better pay and working conditions this year. (Writing by James Macharia, editing by William Hardy)