* Matata Ponyo says Rwandan support for rebels an "open secret"
* Says U.N. must impose sanctions after experts' report
By Daniel Flynn
PARIS, Nov 16 (Reuters) - The prime minister of Democratic Republic of Congo urged the United Nations on Friday to impose sanctions on senior Rwandan officials linked to a bloody insurgency in eastern Congo, or risk losing its credibility.
Augustin Matata Ponyo said the U.N. Security Council must take firm action after a confidential report by a U.N. panel of experts accused Rwandan officials, including Defence Minister James Kabarebe, of arming and supporting the M23 rebel group.
In some of the worst fighting in months, the Congolese army repulsed a second day of attacks by M23 fighters on Friday 30 km (20 miles) north of Goma, the capital of the mineral-rich North Kivu province, scarred by nearly two decades of bloodshed.
Matata Ponyo said the army was determined to resist the rebel onslaught, which he said was aimed at capturing Goma and had already caused large numbers of civilians to flee.
"The involvement of Rwandan officials with these rebels is an open secret," Matata Ponyo said in an interview during a visit to Paris.
"If United Nations singles out Rwanda as a subversive influence in east Congo but it makes no effort to sanction those named in its own report, then it will have a problem of credibility."
U.N. diplomats had earlier told Reuters that the expert panel had urged the U.N. Security Council's Congo sanctions committee at a closed door meeting on Friday to impose sanctions on Kabarebe and other Rwandan officials.
Kigali denies backing Congo's rebels but some Security Council diplomats say its denials are not credible. Rwanda twice invaded its larger neighbour in the 1990s, sparking a lingering humanitarian crisis which has claimed 5.4 million lives.
The diplomats said it was unlikely the Council would agree to add Rwandans to a U.N. blacklist on Congo - subjecting them to an international travel ban and asset freeze - but even proposing such sanctions would send a strong message to Rwanda.
"ATTACK BY A FOREIGN POWER"
Ahead of a meeting with his French counterpart Jean-Marc Ayrault, Matata Ponyo said he wanted to use his visit to convince France - a permanent member of the Security Council - that Rwanda was backing the M23 rebels to gain control over eastern Congo's vast mineral wealth.
"This is not an internal Congolese conflict. It is an attack by a foreign country," he said. "Until the international community understands that, a solution will be slow in coming."
Eastern Congo, ravaged by decades of on-off conflict, was once against plunged into violence at the beginning of the year when hundreds of soldiers defected and launched M23, which says it wants to overthrow President Joseph Kabila.
More than 760,000 people have fled their homes since.
The U.N. experts' report on Rwanda's involvement in the rebellion prompted Belgium to halt all new military aid to its former colony this month, joining a list of donors including the European Union and Washington applying pressure to Kigali.
"The publication of this report should prompt other Security Council members and European countries to take measures in the same direction," Matata Ponyo said. (Reporting By Daniel Flynn; Editing by Pravin Char)