Malians rushed to stock up on petrol and cash on Tuesday after neighbours went ahead with trade and diplomatic sanctions aimed at forcing the military junta to hand over power.

For long one of the most stable democracies in West Africa, Mali has plunged into turmoil since a widely condemned March 22 coup that emboldened Tuareg rebels to seize half the country in their quest for a northern homeland.

They have been joined by Islamists bent on imposing sharia, Islamic law, across the whole of the moderate Muslim state, now the latest security headache for a region battling al Qaeda agents and home-grown militant groups like Nigeria's Boko Haram.

At the request of former colonial power France, the crisis is to be discussed by the U.N. Security Council on Wednesday.

Ivory Coast, from where the land-locked country sources much of its fuel, was among the first to close its borders on Tuesday as part of sanctions including the freeze of Malian funds at the central bank of the West African franc currency zone.

Our bosses told us to let nothing go in or come out without orders from the top ... We've started patrolling to stop all movement of goods, border guard Ben Casaban said by telephone from the border point by the town of Pogo.

Others acted more slowly on the sanction order. Authorities in Burkina Faso said they were preparing steps needed to close the border with Mali, while borer officials in Mauritania and Senegal said they were still awaiting orders.

At garages in central Bamako, residents armed with jerry-cans queued to beat feared shortages which could begin to choke off the economy of Africa's third-largest economy within days.

Cisse Yacouba, a 25-year-old student queuing outside a bank, feared commercial bank funds would dry up soon.

I'm here to withdraw my bursary money, he said. Because of the sanctions, everyone is rushing to get some money because it is certain that there will not be enough.

HERITAGE SITES SEEN AT RISK

The junta, led by the hitherto obscure U.S.-trained Captain Amadou Sanogo, issued a statement late on Monday acknowledging the sanctions and repeating its promise to hand over power to civilians at an unspecified date.

We ask the population to remain calm, the statement on state television said, adding that the priority at the moment remained fighting the rebellion in the north.

While the stated aim of the coup leaders was to give the army more clout to tackle the two-month-old revolt, their power grab triggered a rebel sweep through a northern zone the size of France - in many cases hard on the heels of fleeing army forces.

The Tuareg-led rebel group MNLA says it controls the three main towns in the desert zone - Kidal, Gao and the ancient trading post of Timbuktu - and has stressed it has no intention of pushing further north.

But there is growing disquiet about the role of the local Ansar Dine Islamist group, which, rather seeking to carve out a northern homeland, wants to impose Islamic law across all of Mali. In Gao its members ransacked hotels serving alcohol and told locals that Western-style clothing was banned.

Residents in Timbuktu said on Monday that better-armed Ansar Dine fighters had dislodged MNLA rebels who initially seized the town on Sunday.

A military source said rebels on Tuesday pushed further to the town of Douentza - at the southern extremity of the Azawad territory they see as rightfully theirs - but said the regular army had taken up positions outside the regional centre of Mopti to prevent them going any further.

Mali's neighbours see the exit of the coup leaders as a prerequisite to any regional attempt to halt the rebellion.

Ousted President Amadou Toumani Toure, who had been due to step down in scheduled elections this month, is still in hiding. Neighbours are proposing that a neutral figure be named as interim president before a new attempt to stage polls.

It is unclear what appetite there is in the region for military intervention to secure the south from any further advances and, ultimately, to win back ground from the rebels.

Military chiefs of the 15-nation ECOWAS regional bloc are due to meet on Thursday to agree on paper a force of up to 3,000 troops, but the arduous process of extracting troop contingents from individual countries has yet to begin in earnest.

Over 200,000 Malians have fled their homes because of the fighting, and the pillaging of food, fuel and medical supplies in Gao and other northern towns has worsened their plight.

In Paris, world culture agency UNESCO appealed to warring factions to spare local heritage sites such as Timbuktu's earthen mosques, cemeteries and other legacies of its golden era in the 16th century.

(Additional reporting by Adama Diarra and Tiemoko Diallo in Bamako; John Irish in Paris; Writing by Mark John; Editing by Alison Williams)