U.S. markets started the week lower on Monday as the U.S.-China trade war entered a new phase when tariffs on billions of dollars of products took effect. The Dow Jones Industrial Average fell 181.45 points, or 0.7%, to 26,562.05 after closing at a record on Friday. The S&P 500 lost 10.31 points, or 0.4%, to 2,919.37. The Nasdaq Composite Index reversed earlier loss to rise 6.29 points to 7,993.25.

European stocks also moved lower, with banks and mining shares helping to lead the downdraft as trade worries resurfaced. The Stoxx Europe 600 slipped 0.6% to close at 382.14, after Friday’s gain of 0.4%. Germany’s DAX 30 shed 0.6% to end at 12,350.82, while France’s CAC 40 declined 0.3% to 5,476.11 and the U.K.’s FTSE 100 lost 0.4% to finish at 7,458.41.

Instagram co-founders resign in latest Facebook executive exit

Instagram on Monday said co-founders Kevin Systrom and Mike Krieger have resigned as chief executive officer and chief technical officer of the photo-sharing app owned by Facebook Inc., and plan to leave the company in the coming weeks. They did not give a reason for stepping down, according to the people, but said they planned to take time off after leaving Instagram. The departures at Facebook’s fastest-growing revenue generator come just months after the exit of Jan Koum, co-founder of Facebook-owned messaging app WhatsApp, leaving the social network without the developers behind two of its biggest services.

The departures raise questions about Instagram’s future at a time when Facebook faces its most sustained set of crises in its 14-year history. For much of the past two years, critics have railed against Facebook for being careless with user data and for not preventing foreign interference across its network of more than two billion people. The issues have started taking a toll on Facebook’s business, with the company saying in July that growth in digital advertising sales and in the number of its users had slowed down. Their announcement came after increasingly frequent clashes with Facebook Chief Executive Mark Zuckerberg over the direction of Instagram, Bloomberg reported.

Beijing pushes ahead with opening up its financial sector despite trade tensions

China is moving ahead with planned financial reform, despite pressure from a slowing economy and rising tensions with its largest trading partner. Beijing has taken numerous steps to increase overseas participation in domestic markets and financial businesses. The Shanghai composite has dropped into a bear market — more than 20 percent from a recent high. That comes amid concerns about China’s economic slowdown and renewed pressure from the trade dispute with the U.S. Recent financial reform efforts that Chinese authorities have taken include allowing individual foreign investors in the country to buy mainland-traded stocks, known as A shares, and removing limits of foreign holdings in banks.

While exports and a population roughly four times the size of the U.S. have helped spur China to become the second largest economy in the world, the local stock and bond markets are relatively underdeveloped and isolated from global capital. Beijing would like to boost the prominence of the yuan internationally, attract more foreign capital and manage the hot money flows of its increasingly wealthy population who have limited investment options. However, it’s not clear when announced changes will take effect. In practice, the process could still take longer than stated.