Asian stocks fell, with the regional benchmark index declining the most in six months, as concern grew that the European debt crisis may worsen after Francois Hollande was elected France's first Socialist president in almost two decades.

Samsung Electronics Co, the world's No 1 maker of mobile phones by sales, dropped 1.3 percent in Seoul after US employers added fewer jobs than expected.

Sony Corp sank 4.5 percent, leading losses among Japanese exporters on concern a weaker euro will damp overseas income. Miner and oil producer BHP Billiton Ltd lost 4.1 percent in Sydney as copper and crude futures fell.

"The situation in Europe is tough," said Khiem Do, Hong Kong-based head of Asian multi-asset strategy at Baring Asset Management Asia Ltd. The firm oversees about $10 billion. "Very few nations can stand austerity. If the European Monetary Union stays the same, something has to give."

The Nikkei 225 Stock Average sank 2.8 percent as Japanese markets resumed trading after a four-day weekend. South Korea's Kospi Index slid 1.6 percent and Australia's S&P/ASX 200 Index closed down 2.2 percent, its biggest loss since December.

Volatility surges

Hong Kong's Hang Seng Index declined 2.6 percent, while the Shanghai Composite Index was little changed, slipping 0.07 point to 2,451.95 at the close.

Volatility rose as stocks tumbled. The HSI Volatility Index, a measure of options prices on the Hang Seng, jumped 19 percent to 22.29 for the biggest gain in six months. The Nikkei Stock Average Volatility Index surged 14 percent to 22.58, the highest since March 15.

A US report showed payrolls climbed 115,000 in April, the smallest gain in six months and below economists' estimates for a 160,000 advance.

The jobless rate fell to a three-year low of 8.1 percent as people left the labor force.

Exporters to the United States declined. Samsung Electronics slid 1.3 percent to 1.342 million won ($1,179.63) in Seoul. Li & Fung Ltd, a supplier of toys and clothes to Wal-Mart Stores Inc, sank 5.1 percent to HK$16.32 ($2.10) in Hong Kong. Honda Motor Co dropped 5.6 percent to 2,660 yen ($33.34) in Tokyo.

"In the US, the job recovery is getting sluggish, fueling concern that may have a bad impact on consumer spending and housing markets," said Toshiyuki Kanayama, a market analyst at Tokyo-based Monex Inc.

"There's concern that the European debt problem may get serious. The euro is being sold in the currency market and that's negative for Japanese stocks," Kanayama said.

Japanese exporters also declined after the euro fell to its lowest level against the yen in almost three months as French voters elected Hollande president and Greek voters flocked to anti-bailout parties, stoking concern austerity efforts in Europe may be derailed.

Sony, which gets about 21 percent of sales from Europe, dropped 4.5 percent to 1,213 yen, headed for its lowest close since April 1987. Canon Inc, which counts Europe as its biggest market, dropped 1.9 percent to 3,530 yen.

Hollande, the first Socialist in 17 years to lead Europe's second-biggest economy, pledged to push for less austerity. Hollande's platform calls for policies German Chancellor Angela Merkel opposes, including increased government spending and a delayed deficit-reduction effort.

Woodside Petroleum Ltd, Australia's second-largest oil producer, slipped 2.5 percent to A$34.50 ($35.07). Oil explorer Inpex Corp declined 5.3 percent to 499,000 yen. CNOOC Ltd, China's largest offshore crude producer, decreased 4.2 percent to HK$15.84 in Hong Kong.

BHP dropped 4.1 percent to A$34.57. Rio Tinto Group, the world's No 3 mining company by market value, sank 4.5 percent to A$62. Jiangxi Copper Co, China's biggest producer of the metal, slid 3.3 percent to HK$18.30.