Tunisia's foreign currency reserves rose to 11.389 billion dinars ($6.88 billion) in August, with a Japanese loan helping extend the previous month's recovery after a sharp decline, the central bank said on Wednesday.

But the bank, which kept its key interest rate unchanged at 4 per cent, said the threat to the economy posed by Tunisia's political crisis was increasing.

"The exacerbation of tensions on the national political scene threaten, more than ever, the safety and the fundamentals of the economy," the bank said in a statement, calling on all political parties "to intensify efforts to achieve stability".

The murder of two senior opposition figures this year sparked Tunisia's worst political crisis since Zine Al-Abidine Ben Ali was toppled as president more than two years ago.

The secular opposition threatened on Wednesday to launch more mass protests to force the Islamist-led government to step down.

The central bank said foreign currency reserves on August 31 of 11.389 billion dinars was the equivalent of 104 days of imports. The figure was up on the 10.300 billion dinars at the same point last year.

The bank said it raised 22.4 billion yens (376 million dinars) on August 7 on the Japanese domestic market in the form of a samurai debenture loan with the guarantee of the Japanese Bank for International Cooperation.

In June, foreign currency reserves fell to just 94 days' of imports, for the first time below the 100-day level the central bank considers adequate. - Reuters