UPDATE 2-China refinery runs rise at slowest pace in 15 mos

(Adds analyst comment, write throughout)

By Chen Aizhu

BEIJING, Dec 13 (Reuters) - China's refinery runs rose 3.8 percent in November, their weakest annual rise in 15 months, data showed on Thursday, a possible sign that mainstream refiners are failing to build new capacity fast enough to meet demand.

Following a months-long fuel crisis that prompted a 10 pecent increase in motor fuel prices last month and heavy pressure from Beijing for state-owned refiners to step up production, output by those plants showed only a 4 percent rise versus October, according to data from the National Bureau of Statistics.

November refinery throughput of 27.67 million tonnes (6.73 million barrels per day) was likely curbed in part by maintenance at a top plant, but may also point to capacity limitations in the downstream sector of the world's second-largest oil consumer.

While many analysts say refineries run by the duopoly of Sinopec Corp (0386.HK) and PetroChina (0857.HK) were likely choking back operations earlier this autumn to avoid growing losses in the face of near $100 crude, most believe they are now running flat out after being bending to Beijing's will.

"I trust that most of the Sinopec plants were trying to boost production," said Yan Kefeng, of Cambridge Energy Research Associates. "Their operations ratios were already very high."

The data excludes most small, privately owned "teapot" refiners, most of whom have shut down or deeply cut operations as they suffer losses from importing costly fuel oil and selling diesel or other fuels at low, regulated retail prices.

That suggests the mainstream players are struggling to fill the gap, explaining the surge in diesel imports -- and suggesting that the heavy demand could last for several more months.