ULSAN, June 10 — Defiant South Korean truckers embarked on broader and more aggressive strike action today, threatening to severely curtail deliveries of raw materials for semiconductors and petrochemical products.

Entering its fourth day, the strike protesting soaring fuel costs halved production at Hyundai Motor Co's biggest factory complex yesterday and has disrupted shipments for a range of companies including steelmaking giant POSCO .

Container traffic at ports has also slowed sharply. At Busan port, which accounts for 80 per cent of the country's container activity, traffic was down to a third of normal levels today, a government official said.

At Incheon port, it has fallen to 20 per cent of normal levels while at the port for Ulsan, the industrial hub where much of the strike action has occurred, container traffic has been completely suspended since Tuesday.

Some 7,500 members, or about 35 per cent of the Cargo Truckers Solidarity union, are expected to be on strike today, the transport ministry said. The government estimates that about 6 per cent of the country's 420,000 truck drivers belong to a union.

The union has contended that the numbers on strike are much higher than government estimates and that many non-union truckers are also refusing to work.

South Korea is a major supplier of semiconductors, smartphones, autos, batteries and electronics goods and the latest industrial action further raises uncertainty over global supply chains already disrupted by China's strict Covid restrictions and Russia's invasion of Ukraine.

Faced with one of his first big economic challenges, new President Yoon Suk-yeol has taken what he calls a neutral stance, saying the government should not be involved too much.

That has alarmed some observers, who say Yoon's remarks could hinder the government's ability to come up with a solution.

"The government needs to review the union's demands. They don't need to accept them all, but I think they could make the situation a bit easier if they could consider giving out subsidies so truckers can deal with soaring fuel prices," said Shin Se-don, an economics professor at Sookmyung Women's University.

The union said a meeting with the government today ended without an agreement and they would meet again tomorrow.

Hyundai hindered

Share prices of major companies have been little affected on the view that the firms have sufficient inventories to ride out the strike for the time being.

Kim Gyeong-dong, a trucker union official, said the union ran out of funds to finance the strike on Thursday and that it was unlikely that the strike could last another 10 days.

Some companies were looking to make new contingency plans.

"If the strike continues next week, then we need to reassess our handling of shipments," said an official at a major South Korean electric vehicle (EV) battery maker, declining to be identified due to the sensitivity of the subject.

Outside factory and ports, union members were not physically blocking gates but would flag down approaching vehicles driven by non-union truckers, asking them not to proceed and cooperate with the strike. Police were present, however, and trucks wanting to be let through would not be stopped.

Among new actions, truckers plan to stop shipments of raw materials for semiconductors that are produced in Ulsan, Park Jeong-tae, a senior truckers union official, told Reuters on Friday.

Chipmakers Samsung Electronics Co and SK Hynix declined to comment.

Park added union efforts had cut the number of vehicles entering a big Ulsan petrochemical complex to one-tenth of normal levels and that it was planning similar stringent strike action at other petrochemical complexes across the country.

Some 1,000 truckers were protesting outside Hyundai Motor's main complex in Ulsan today, a Reuters witness reported.

"There are some disruptions to our production due to the truckers strike, and we hope production would be normalised as soon as possible," a Hyundai spokesperson said.

Hyundai normally makes about 6,000 vehicles a day at its plants in Ulsan.

The truckers, regarded as self-employed contractors in South Korea, are seeking pay increases and a pledge that an emergency measure guaranteeing freight rates would be extended. The emergency measure was introduced during the pandemic and is due to expire in December.

Police said around 30 union members have been arrested so far. — Reuters