West African presidents on Thursday threatened tougher action against coup leaders in Mali and Guinea-Bissau who have resisted efforts to fully restore civilian rule.

Guinea-Bissau's ruling military junta, hit with EU sanctions on Thursday, has refused to quit power, while the junior officers who toppled Mali's government in March are still flexing their authority despite formally giving way to a new government.

Regional leaders from the Economic Community of West African States (ECOWAS) meeting in Senegal's capital on Thursday said the coup leaders faced new measures if they continued to defy 15-nation bloc's demands.

Ivory Coast's President Alassane Ouattara, the ECOWAS chief, condemned "the refusal of the Mali and Guinea-Bissau juntas to accept ECOWAS decisions," in opening remarks at the summit.

"The defiance of the two military juntas is leading us to take further steps to implement our organisation's decisions," he added.

The Ivorian leader said the talks were crucial as they are coming "at a time when the situation in Mali is deteriorating, and frequent about-turns by the Guinea-Bissau junta are delaying the return to constitutional order."

The coup leaders came under additional sanctions Thursday as the European Union slapped an assets freeze and travel ban on six soldiers.

In Mali, a group of soldiers ousted president Amadou Toumani Toure on March 22, but coup leader Captain Amadou Sanogo agreed last month to an ECOWAS-brokered deal that led to the swearing in of a new transitional government.

Although he has formally quit power, Sanogo remains an influential political force.

He has refused ECOWAS demands for elections within 12 months and rejected plans to send foreign troops into northern Mali, captured by a loose coalition of Tuareg and Islamist rebels after the coup.

In Guinea-Bissau, plans for a return to constitutional rule after an April 12 coup by army chief Antonio Indjai are clouded in ambiguity.

The junta initially accepted a 12-month transition programme brokered by the region, however three days later talks in Banjul collapsed and ECOWAS slapped the coup leaders with sanctions, saying Indjai was not willing to negotiate.

Kadre Desire Ouedraogo, president of the ECOWAS Commission called for a harder stance by regional leaders against both Mali and Guinea-Bissau.

"The region cannot tolerate this perpetual defiance of the Bissau-Guinean soldiers who by disregarding the constitution are trying to impose their will on the people."

Senegal's President Macky Sall opened the meeting of ECOWAS leaders, aimed at "synchronising the regional response" to the political crises.

"Recent developments in Mali are a source of grave concern. Africa and the world are watching us," he said in his opening speech.

Tensions flared again early this week as elite "Red Beret" paratroopers who had remained loyal to the ousted president Toure attempted a counter-coup against the former junta, leaving 22 people dead, according to hospital sources.

At the talks was Mali's interim president Dioncounda Traore, appointed to lead the country back to democracy after the coup.