Major European and Saudi banks have stopped dealing with Sudan, diplomatic and other sources say, adding to the sanctions-hit country's isolation and further straining its indebted, cash-starved economy.
While Khartoum blames increased "pressure" from a US trade embargo first imposed 17 years ago, a US official said there had been no change in policy from Washington, according to the AFP news agency.
The move by the European banks appears to reflect an increasingly cautious attitude by financial institutions which do not want to risk being found in violation of US sanctions, a Western diplomat said.
Most of the accounts or money going out of Sudan, it's completely frozen.
"I think this is something actually mushrooming," he said of the risk aversion.
Germany's Commerzbank was the latest to sever its Sudan connection, according to diplomats.
The bank had no comment when reached by AFP.
In 2012, the British banks HSBC and Standard Chartered were fined $1.92bn and $667m respectively for violations that included sanction breaches with Iran and Sudan.
That same year, Dutch bank ING agreed to pay $619m to settle US government accusations that it conducted banned transactions involving Sudan and other countries.
In 2010, Wikileaks published secret US diplomatic cables that recounted conversations with the chief prosecutor of the International Criminal Court, accusing President Omar al-Bashir of stashing up to $9bn in UK bank accounts.
"Ocampo reported Lloyds bank in London may be holding or knowledgeable of the whereabouts of his money," a US official in the cable says. "Ocampo suggested exposing Bashir had illegal accounts would be enough to turn the Sudanese against him."
Lloyds responded by saying it had no evidence of holding funds in Bashir's name.
US authorities are also probing the French banks Societe Generale, BNP Paribas and Credit Agricole for alleged embezzlement and violation of sanctions against countries like Iran and Sudan, a source close to the matter said last week.
The European Union itself has no embargo against Sudan, whose government seized power 25 years ago in a coup.
But European banks with US branches or business "are closing any Sudanese accounts and won't even process payments from Sudan", the diplomat said.
This affects private and government transactions.
A local banker, who asked not to be identified, said that starting this month Saudi banks too had stopped dealing with the African nation.
Meanwhile in Khartoum, President Bashir met with opposition leader Hassan al-Turabi on Friday for the first time in 14 years as part of a political and economic “renaissance” the president announced in January.
Turabi was a key figure behind the 1989 coup which brought Bashir to power but the two fell out leading to Turabi been dismissed from the ruling National Congress Party a decade after the coup.