The death toll from the worst floods in half a century to hit Thailand continued to climb Tuesday as the government rushed to shore up defenses around the capital.

The country’s Flood Relief Operation Command reported that flood defense measures in low-lying Bangkok have held and that the bloated Chao Praya River has not risen any farther.

There had been fears that further heavy rain over the weekend, combined with the spring high tides, would overwhelm parts of the city.

“Bangkok is not safe yet, but it is not critical,” Bangkok Gov. Sukhumbhand Paribatra said. He said the next 48 hours will prove key.

Millions of sandbags are being put in place to protect the northern part of the capital.

So far, 315 people have been killed during months of monsoon rains across Thailand, with more than 8.6 million in 61 provinces affected by the rising floodwaters.

State-run news agency MCOT broadcast images that show entire streets underwater. Prime Minister Yingluck Shinawatra took a helicopter tour to inspect some of the hardest-hit areas, it reported. The floods are proving a challenge to her new government.

The Thai finance ministry says overall damage from the floods could be more than $2 billion, with the worst possibly to come.

More than 500,000 square kilometers — an area the size of Spain — have been affected by the floods in Thailand, Cambodia, Vietnam and Laos, according to CNN meteorologist Jenny Harrison.

Floods are an annual occurrence in the region, but they have been particularly acute this year.

CNN’s Kocha Olarn contributed to this report.