China is apparently dragging its feet in punishing those involved in the sinking of a South Korean Coast Guard vessel which took place during a crackdown on illegal fishing, Seoul officials and observers said Tuesday.

In early October, the 4.5-ton speed boat that was engaged in an operation to capture fishing boats operating illegally in waters off the country's west coast sank when a larger Chinese vessel rear-ended it. There were no casualties in the incident that the Coast Guard views as an "intentional" collision.

South Korea's foreign ministry immediately called in Chinese Ambassador Qiu Guohong and demanded efforts to prevent a recurrence. China said that an investigation is underway and it will deal with the matter in accordance with law.

"We have made inquiries about the latest developments through diplomatic channels but not received any answer yet," a government official said on condition of anonymity.

Observers worry that Chinese authorities are not active enough to resolve illegal fishing, which has been a major drag on bilateral ties between the two neighbors.

In the wake of incident, Seoul beefed up its response to illegal operations carried out by Chinese boats.

Recently, South Korea's Coast Guard used machine guns to chase Chinese fishing boats operating illegally, an act that drew strong outcry from China, calling it a "violent" crackdown. (Yonhap)