Residents of Mehar in Pakistan's Sindh province, with their animals and belongings, leave in fear of approaching flood waters on Saturday. (Athar Hussain/Reuters)

People in parts of Sindh province in southern Pakistan are bracing for more floods as water threatens to pour into more towns and villages.

In Mehar, a community in the Dadu district, residents are hoping a mud dike will protect the area from flood waters.

"Those waters have advanced right up to the dike and there are people monitoring that night and day for breaches," CBC's Tom Parry said from Mehar.

"Every once in a while the water starts to break through and the men have to scramble to try and patch that up."

Parry said people in Mehar are trying to protect their homes by building brick walls in front of door frames in hopes the new walls will block the water if the dike is breached.

But some people aren't taking chances and are leaving for higher ground.

[an error occurred while processing this directive]

"It’s beginning to look like a ghost town," CBC's Nahlah Ayed said Wednesday.

"Really, the only people who remain are the men. They have sent their families away, their children, their women and have remained there essentially … to try to protect their own property."

Other towns in the area, including Johi and Dadu, are also at risk, a local newspaper reported.

More than 1,700 people have died and the UN estimates almost 21 million people have been affected by the floods in Pakistan, which began about six weeks ago in the northwest.

Valerie Amos, the newly appointed United Nations emergency relief co-ordinator, arrived in Pakistan on Tuesday to see the devastation and call for more aid.

“The floods here in Pakistan have affected almost 21 million people — it is one of the biggest humanitarian crises the world has seen,” Amos said.

She called for increased international support for the South Asian nation, saying donations seem to have hit a plateau, with new donations dropping to "just $20 million US over the last two weeks."

"It is both worrying and disappointing that this is happening when the needs continue to rise and the suffering is still so evident," she said in a statement.

With files from CBC's Tom Parry