By Josie Cox 

Talks between Greece and its European creditors collapsed over the weekend, sending shock waves through global markets Monday.

By mid afternoon, the Stoxx Europe 600 index was trading around 1.5% lower, weighed down by a 1.9% slide on Germany's DAX-30. In the U.S. the S&P 500 was 0.9% lower.

Athens' main stock exchange was slightly more than 5% lower on the day, led by a steep decline in banking stocks.

The falls came after European officials on Sunday dismissed the Greek government's latest proposals, describing them as "vague and repetitive." Last week the International Monetary Fund pulled out of the Greek bailout talks, citing lack of progress, already making markets jittery.

"We have always argued that a Greek deal would only occur at one minute to midnight," Rabobank rates strategists wrote in a note. "Yet it now looks like 23:58 and counting."

Shares in Greece's Alpha Bank AE, Eurobank Ergasias SA, National Bank of Greece SA and Piraeus Bank SA were all down between 7.5% and 14% by mid afternoon. Monday's drop means they have now all declined more than 20% since the start of June and between 35% and 65% since the start of the year.

Greek bonds also tumbled, sending the yield on the country's two-year debt up to almost 29%, close to 3 percentage points higher on the day and at a level last seen in April. Yields rise as bond prices fall.

Concerns about Greece also hit the euro, which was trading around 0.3% lower Monday, at around $1.123 to the buck. Several strategists said that the currency would likely remain under pressure until a resolution is found.

"Creditors are getting tired with the negotiations," said Eirini Tsekeridou, an analyst at Swiss private bank Julius Baer. Ian Williams, economist and strategist at brokerage Peel Hunt, said that hopes for a compromise are diminishing, while strategists at BNP Paribas wrote in a note that "the risk of unfavorable scenarios, such as a default, has undoubtedly risen."

Attention this week will be on Thursday's Eurogroup meeting, ahead of a Brussels summit on June 25, and a hefty Greek debt repayment deadline on June 30.

Credit Suisse economists said Thursday's meeting would likely be "one of the last chances to rubber stamp an agreement between Greece and its creditors."

"With the Greek government still living in its own world, hopes for a solution are evaporating," said Demetrios Efstathiou, a senior economist at Standard Bank. He added, however, that he still thinks an agreement will be reached, but only "at the very last minute" and "not a minute earlier."

Back in debt markets, the yield on the 10-year German government bond was around 0.03 percentage point lower at around 0.81% by midday.

Yields on Spanish and Italian 10-year debt, which some strategists say could be most affected by a Greek default, were higher at around 2.36% and 2.32% respectively.

"From a market perspective the concern is that if Greece was to default and/or exit, then it might encourage others to do the same," said Gary Jenkins, a credit strategist at London-based asset manager LNG Capital. That, he said, "puts the entire eurozone project at risk of collapse."

In Asia, the Nikkei ended Monday marginally lower, marking its fifth loss in the past seven sessions, with strategists also citing tension over unfruitful Greek debt talks as well as fears over the implications of a U.S. interest rate increase in coming months.

Write to Josie Cox at josie.cox@wsj.com

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