* Massive platinum strike starts
* Half of world platinum production hit
* Police out in force near Lonmin's Marikana mine
* Court halts threatened stoppage in gold sector
RUSTENBURG, South Africa, Jan 23 (Reuters) - South Africa's hardline Association of Mineworkers and Construction Union (AMCU) began a strike over pay in the platinum sector on Thursday, bringing mines that produce half the world's platinum to a standstill.
Members of AMCU, the platinum sector's main union, downed tools at Anglo American Platinum, Impala Platinum and Lonmin, the top three producers of the metal used in emissions-capping catalytic converters in cars.
"The strike has started at all operations," AMCU spokesman Jimmy Gama said.
The union, whose emergence two years ago has thrown South Africa's mining labour relations into turmoil, has as many as 100,000 members on the platinum belt, 120 km (70 miles) northwest of Johannesburg.
It was unclear if they had all heeded the call to strike.
It is also hard to estimate the duration of the stoppage amid recent signs of divisions in AMCU's ranks.
Dissidents said this week they planned to form a rival union, accusing AMCU's leaders, especially president Joseph Mathunjwa, of recklessly pursuing a damaging strike they say many miners do not want and cannot afford.
But AMCU activists in the nearby city of Rustenburg on Wednesday night said the workers remained committed to a stoppage under the battle cry of a "living wage".
AMCU is seeking a more than doubling of the basic entry-level wage from Amplats and Lonmin and smaller but still steep hikes from Implats. The companies are offering increases of 7.5-8.5 percent, well above the 5.4 percent inflation rate.
The firms were battered by wildcat strikes in 2012 rooted in a turf war between AMCU and the National Union of Mineworkers (NUM) in which dozens of people were killed. They say they cannot big pay hikes.
Mindful of the bloodshed and violence of the last two years, police deployed in force, especially near Lonmin's Marikana mine where 34 striking miners were shot dead by police in August 2012.
AMCU had also planned to strike at several gold mines on Thursday but a court ruled the action be suspended pending a review of its legality.