Updated

South Korea's ruling party has won most of the seats at stake in legislative by-elections, cementing its majority and giving a boost to President Park Geun-hye's embattled conservative government after April's ferry disaster.

The National Election Commission said Park's Saenuri Party has won 10 of the 15 vacant seats in the National Assembly and has a comfortable lead in one other district.

Wednesday's elections were considered a gauge of public sentiment toward Park's administration after her approval rating plummeted over the government's handling of the ferry sinking, which left more than 300 people dead or missing.