London's leading shares nose-dived on Monday amid rising fears of a debt default by Greece.
The FTSE 100 Index tumbled 147 points to 6,607 in the first hour of trading as traders mulled latest developments in the stand-off between Athens and its creditors.
Greece has called a referendum on reform proposals by the International Monetary Fund (IMF) and other creditors after refusing to accept them in talks in Brussels.
Greek banks are to remain closed today and capital controls will be imposed, Prime Minister Alexis Tsipras revealed on Sunday.
It followed news that the European Central Bank (ECB) won’t increase emergency funding to the country, which is due to repay around £1.1bn to the IMF on Tuesday.
Default would move it closer to ejection from the euro. While cash machines are being kept stocked, there were long queues to make withdrawals.
Greece’s banks are set to stay closed until July 7, two days after its people go to the polls to vote on a bailout deal tabled by creditors.
PM Tsipras described the proposal as "an insulting ultimatum" and is hoping a strong no-vote will strengthen his hand in further negotiations.
The Greeks rejected a five-month extension to Greece's bailout deal in exchange for reforms.
Analysts said a no-vote in the Greek referendum would represent a rejection of the euro, but a yes vote was more likely.
Chris Beauchamp at spread-betting firm IG said: "Time has almost run out to keep Greece in the Eurozone, but even now it is perhaps unwise not to discount the possibility of an emergency package that will avert disaster."
Oil services group Lamprell (LON:LAM) fell 1.5p to 150.5p after reporting some delays in securing contracts, although it said trading was otherwise strong.
Shares of precious metal miners rose as investors worried about the Greek situation sought havens.
Randgold Resources (LON:RRS) gained 31p to 4405p and Fresnillo (LON:FRES) lifted 3p to 701p.
At the other end of the scale, tour operators and airlines fell following the attacks on holiday makers in Tunisia. TUI (LON:TUI) was 91p off at 1,022p and BA and Iberia owner IAG (LON:IAG) dropped 22.4p to 492.1p. Thomas Cook (LON:TCG) shed 9.7p to 134.5p and EasyJet (LON:EZJ) reversed 47p to 1,530p.