There appears to be no clear leader in Scotland's independence battle, just four days before the referendum.

Surveys for two Sunday papers are predicting a "No" vote, while another expects a breakaway.

The Observer newspaper, gives the "No" campaign a six point lead - 53% to 47%. A poll carried out for The Sunday Times newspaper, however, has "No" on a narrow lead on 50.6% compared to "Yes" on 49.4%.

A poll for the Sunday Telegraph however showed support for independence at 54%, a nine-point swing from their last online poll, with support for the "No" campaign at 46%.

But the poll's sample size - 705 people - means its margin of error is higher than most surveys. Polling expert John Curtice said the poll came with "a substantial health warning".

Reacting to the latest snapshots of public opinion, Blair Jenkins, chief executive of Yes Scotland, said that "the polls show that the referendum is on a knife-edge.

"There is everything to play for, and this will spur on everybody who wants and is working hard for a 'Yes' to redouble their efforts."

The latest polls came after First Minister Alex Salmond hit out at banks and businesses that have warned about the effects of independence.

Deutsche Bank said a "Yes" vote could be a mistake akin to those that sparked the Great Depression, while three more retailers said customers would face higher prices.

Six telecoms companies also released an open letter warning such an outcome could mean increased costs in the industry.