By Kwasi Kpodo and Loucoumane Coulibaly

ACCRA and NOE, Ivory Coast (Reuters) - Ghana has promised to help investigate attacks in Ivory Coast that Ivorian officials say were launched by supporters of former President Laurent Gbagbo exiled in the neighboring state.

Ivory Coast closed its border with Ghana on Friday following deadly armed raids on police and army installations in a border town and in its commercial capital Abidjan, further worsening relations between the world's two biggest cocoa growers.

"The government of Ghana remains determined and resolute that the two countries jointly investigate these occurrences to our mutual benefit," Ghana's foreign ministry said in a statement late on Monday.

"Ghana will not allow the hospitality we offer to refugees ... to be construed as providing an opportunity for planning and executing any actions to undermine the sovereignty, peace and reconciliation effort," it said.

Eight people, including six attackers, were killed during what were the first such raids since August, when gunmen launched near-daily attacks on security forces.

Ivory Coast has blamed Gbagbo's supporters, both in Ivory Coast and abroad, of planning the attacks, raising fears of renewed instability a year after a brief civil war killed more than 3,000 people after Gbagbo refused to recognize the victory of rival Alassane Ouattara in a presidential election.

Gbagbo was captured during fighting in Abidjan last year and is awaiting trial at the International Criminal Court on charges of crimes against humanity. Many of his top allies are living in exile, including in Ghana.

Ivory Coast's Interior Minister Hamed Bakayoko told Reuters on Friday that last week's raid was "organized, ordered, and executed" from within Ghana [ID:nL5E8KLMI2]. Gbagbo's political allies have denied any role in the attacks.

Last month Ghana arrested Gbagbo's former budget minister, Justin Kone Katinan, - one of around two dozen members of the former regime sought under international arrest warrants issued by Ivory Coast last year.

However, a Ghanaian court freed Katinan on 50,000 cedi ($26,178) bail on Tuesday pending his extradition hearing.

Ivory Coast announced late on Sunday that it would reopen its airspace to flights from Ghana but kept its land and sea borders shut, blocking a highway that is the main transportation route along the Gulf of Guinea, stretching from Ivory Coast to Nigeria.

Hundreds of trucks are stuck at the border near the Noe, some with fresh produce rotting in the equatorial heat.

"The state needs to find a way to let us through. We are the innocents here," said Siaka Sekongo, who was hauling soap to Ghana when Ivory Coast closed the border.

($1 = 1.91 cedis)

(Additional reporting by Clair MacDougall in Accra; Writing by Joe Bavier; Editing by Robin Pomeroy)