Core government bond yields across all maturities hit new record lows after US President Donald Trump abruptly ended a trade truce with China, announcing tariffs on another $300 billion of its goods which prompted a selloff in global equities.
The yield on the benchmark German 10-year note fell below -0.50 bps for the first time. Germany's 30-year bond yield briefly dropped more than eight basis points to hit -0.006%.
That left the entire German yield curve in negative territory for the first time. The 30-year yield had been as high as 0.89% as recently as January.
"If Trump is upping the ante this isn't great for global growth or trade and reinforces expectations that the ECB will do something," said Matt Cairns, rates strategist at Rabobank.
Money markets moved to price in a 100% chance of a 10 basis point rate cut by the ECB at its next meeting.
The bond market's huge rally in 2019 shows little sign of abating, with investors flocking into fixed income assets, particularly those with a top rating, on the first sign of weakness in the global economy or an escalation in the US-China trade war.
TradeWeb data on Thursday showed that the pool of euro zone government bonds with negative yields surged in July to 4.8 trillion euros or around 60% of the total, the highest proportion since August 2016.
The share of euro zone government bond yields trading below the European Central Bank's -0.4% deposit rate also increased, rising to 42% from 36% a month earlier.
Thursday's announcement extends Trump's trade tariffs to nearly all of the Chinese goods the United States imports. China's foreign ministry said on Friday it would have to take countermeasures and doesn't want a trade war, but isn't afraid of fighting one.
Analysts say the tariffs increase pressure on the US Federal Reserve to ease policy, with the market now pricing in a 60% chance of a 50 basis point cut by the October meeting.
The US 10-year Treasury yield dipped as low as 1.83% on Friday, from above 2.06% before Trump's announcement.
The Fed cut rates by 25 bps for the first time since 2008 on Wednesday but struck a less dovish tone than many investors had expected.
Other core euro zone bond yields were between two and five basis points lower.
US non-farm payrolls data showed that jobs growth slowed in July -- the 164,000 job gains were in line with economists' expectations -- and manufacturers slashed hours for workers.
The market was little moved after the data, however, with all the focus on Trump's tariff threats and the subsequent move by investors to snap up even more government debt.
"Investors were already scrambling for yield ahead of the summer drought before Trump fuelled the rally," Commerzbank analysts wrote to clients.
Trump is scheduled to make a statement on trade with the European Union at 1345 EST (1745 GMT) on Friday, based on daily White House guidance.