(CNN) -- As filthy floodwater continued to seep towards central Bangkok, Thailand's Prime Minister laid out a three-point plan to get the country back on its feet after the worst flooding in 50 years.





Immediate aid will be issued to people whose homes and businesses have been destroyed by the deluge which has claimed more than 500 lives since July, Yingluck Shinawatra announced Tuesday.





"This disaster is the biggest that we have ever met. We're trying to cope with situation and help as much as we can," she said. "We can't stop all flooding but we will try to reduce the impact."





Aid packages will be offered to people to help restore homes and businesses as part of a short-term recovery plan over the coming year. Details are expected to be announced next week.





Longer-term plans include the formation of two committees, one to oversee reconstruction and future development and the other to manage water resources.





Yingluck acknowledged criticism of the official response to the disaster by setting herself a deadline of one year to win back public confidence.





The prime minister's promises came as murky waters continued to move towards Bangkok's city center.





"The situation is quite serious. The water is making ground slowly but surely towards the heart of Bangkok," flood relief co-ordinator Rungsun Munkong told CNN.





He said thousands of people were refusing to leave their homes despite orders to evacuate to outer provinces.





"I believe thousands of people are in their homes and are still not evacuating," Rungsun said. "(They) possibly will be stranded with little food and water as time goes by."





Relief workers, distributing aid to evacuation centers in central Bangkok, said they were struggling to reach residents determined to wait out the crisis in tower blocks.





"I think it will be difficult down the road to get help to these people," Rungsun said. "People need clean water, that's the first important thing. Cooked ready-to-eat food is also quite important, baby milk and so on."





Thailand has been inundated with its worst flood in half a century, affecting at least 25 of the country's 77 provinces.





More than 500 people had been killed in the deluge according to figures released Sunday by the country's interior ministry.





A Thailand Disaster and Mitigation Department report, issued Sunday and reported by MCOT, estimated about 3.1 million people have been affected and 4 million acres of farmland have been damaged. Moreover, the department said two people are believed missing and about 75 highways have closed.





In the provinces of Nakhon Sawan and Ayutthaya, cleanup efforts were under way.





On Sunday, the Prime Minister Yingluck Shinawatra visited Nonthaburi, near Bangkok. There, the government provided 100 boats to help transport people and disperse relief supplies after requests by local officials, according to MCOT.





Despite public criticism of the government's overall response, Yingluck said she would not shake up her Cabinet -- in the short-term, at least. She explained that the focus first is to address the situation, with a full evaluation and possible shuffling to be done after the crisis abates, reported MCOT.





Floods are an annual occurrence in the country but have been particularly acute this year, and some residents and analysts have criticized the government's response.





"Now the government is sending a mixed signal that the situation is fine, but the truth is it the situation far from over," political analyst Supong Limtanakul told CNN. "It is a slow suffocating death of (the) Bangkok business area."





The city's main airport and two large industrial sites are also at risk, Supong said.





Supong said the government did not have enough resources to deal with floodwaters, noting that officials had recently asked the private sector for water pumps to help drain water out of Bangkok.





M.R. Sukhumbhand Paribatra, Bangkok's governor, told MCOT that it may take up to two weeks to drain water out of Bangkok's main roads, and months to drain water from smaller roads.





CNN's Kocha Olarn
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