JOHANNESBURG, May 26 (Reuters) - Ivanhoe Mines ( IVPAF )

said on Monday it had suspended its output forecast for this

year after seismic activities at its giant copper mine in the

Democratic Republic of Congo halted underground mining

operations.

The Canadian miner said guidance for the Kamoa-Kakula mining

complex, initially set between 520,000 and 580,000 metric tons

of copper, and its planned ramp up at the smelting plant, had

been withdrawn.

Ivanhoe shares tumbled as much as 15.6% in morning trade in

Toronto. The stock is down 36% so far this year, according to

LSEG data.

The Vancouver-based miner said on May 20 it had initially

suspended some mining activities in a section of its Kakula mine

after seismic activities or underground tremors. The company

said on Monday that it was forced again to suspend operations

over the weekend due to seismic activities over the past few

days.

"Seismic activity at the Kakula underground mine has

continued to occur intermittently over the past few days,"

Ivanhoe said.

The tremors have also affected underground infrastructure,

including water pumping and there has been an increase in water

inflow levels into the Kakula mine, the miner said.

The operations at the adjacent Kamoa mine had not been

interrupted, it said.

The suspension of production guidance "leaves uncertainty as

we await further updates to determine the potential impact on

production," RBC Capital Markets said in a note.

On Friday, Ivanhoe contradicted joint venture partner Zijin

Mining about the extent of problems at the mine.

The Chinese miner said on Friday in a public filing that the

seismic activity could affect this year's planned copper

production, a statement that Ivanhoe disputed on the grounds it

was still conducting investigations.

The Congo mines produced about 437,000 metric tons of the

metal last year.

On Monday Ivanhoe said it and Zijin would work together to

bring the Kakula mine back into production as soon as possible.