Media playback is unsupported on your device Media caption An opposition politician detonated a tear-gas canister as voting began

South Korea's parliament has ratified a free-trade deal with the US, after years of wrangling over the issue.

Members of the ruling Grand National Party, which has a majority, convened to force the bill through in a 151-7 vote.

Most of the opposition abstained. One politician set off a tear-gas canister before the vote and others jeered as the bill passed.

The US Congress ratified the deal last month and it has now been made law.

It is America's largest free-trade deal since the North American Free Trade Agreement with Canada and Mexico in 1994.

The bill - first agreed in 2007 - was ratified in a snap parliamentary session.

"We have decided to push the free trade deal through parliament by voting, as it is almost impossible to reach a compromise with the opposition," GNP politician Park Jun-sun told local media.

It is expected to increase US exports to the Asian economy by as much as $10bn (£6.5bn). There was almost $90bn in trade between the US and South Korea last year.

But South Korean farmers and some workers oppose the deal, saying it threatens their livelihoods and favours US workers.

Protests took place outside parliament as the deal was passed.

The presidential office welcomed the deal and promised to address workers' grievances.

"The government will actively pursue measures for farmers and smaller business owners... in policies and continue to put together measures to strengthen their competitiveness," said presidential press secretary Choe Guem-nak.

The BBC's Lucy Williamson in Seoul says passing it was seen as a risky move because with elections due next year, many voters already say they feel alienated by the big parties' bullish tactics.