It was a bad start to another week in the markets. Asian shares slid to their lowest levels since 2011 on Monday amid weak U.S. economic data and a massive fall in oil prices that fueled further worries about a global economic downturn.

MSCI’s broadest index of Asia-Pacific shares outside Japan fell to its lowest since October 2011 and was last down 0.5 percent.

Japan’s Nikkei 225 fell 1.9 percent to 16,814.10 and Hong Kong’s Hang Seng lost 1.6 percent to 19,210.83. The Shanghai Composite slipped 0.4 percent to 2,890.93 and South Korea’s Kospi dropped 0.5 percent to 1,868.86. Australia’s S&P/ASX 200 fell 1 percent to 4,846.00. Shares in Taiwan, New Zealand and Southeast Asia also fell.

The nuclear deal between Iran, the U.S. and five other world powers took effect over the weekend, ending a European oil embargo on the world’s seventh-largest oil producer, reinforcing expectations that prices will remain weak as supply overwhelms demand. Benchmark U.S. crude was down 26 cents to $29.16 a barrel in electronic trading on the New York Mercantile Exchange. Brent crude, a benchmark for international oils, fell 26 cents to $28.68 per barrel after falling $1.94 to $28.94 in London on Friday.

Currencies

The dollar rose to 117.15 yen from 117.00 yen on Friday. The euro fell to $1.0904 from $1.0913. while the Canadian dollar hit its lowest level in nearly 13 years. The safe-haven yen gave up some of its gains after having risen to a five-month high of 116.51 to the dollar on Friday ending the session at 117.21.

The euro also edged down against the dollar to $1.0893and the Chinese yuan rose 0.6 percent in the offshore trade to 6.5808 to the dollar.