NIAMEY (Reuters) - Niger's Prime Minister Ali Mahaman Lamine Zeine said on Saturday that Benin's blockade of Niger's oil exports, imposed in response to a border closure, violated trade agreements between the two countries and with Niger's Chinese partners.

Speaking at a press conference in the capital Niamey, Zeine said Niger could not fully reopen its border with Benin for security reasons, in comments that escalate a dispute that saw Benin this week block supplies of Niger's crude oil to ships in its port.

The blockade jeopardises landlocked Niger's plan to start crude exports under a $400 million deal with state-owned oil major China National Petroleum Corp, important because Niger has said it would use funds from the export deal to fund bond payments missed while under regionally imposed sanctions.

Zeine said the blockade was in violation of about a dozen accords signed by Benin, Niger and the Chinese side relating to a recently launched, PetroChina backed pipeline linking Niger's Agadem oil field to the Benin port of Cotonou.

But Benin has said it will only back down once Niger reopens its border to goods from Benin and normalises relations.

Zeine said one of the oil export accords stipulated that Benin could not unilaterally modify or limit the agreements in any way possible without the consent of the other parties.

"This means that the country agreed not to take any decision that would stop the flow of Niger's crude oil to the international market. This is serious. This is a violation of an agreement," he said at a press conference.

Relations between the two countries have been strained since a July 2023 coup in Niger led the West African regional bloc ECOWAS to impose strict sanctions for more than six months.

What happens next is unclear. Zeine said Niger would not comply with Benin's request to fully reopen its border.

"In Benin's territory, there are bases where in some, terrorists are trained to come and destabilise our country. So, it is for simple security reasons that we decided to maintain the border closure," Zeine said, without giving any further detail on the allegations.

"We'll reopen the border when we are certain that our territory is secured."

Niger is battling a decade-old insurgencies led by armed groups linked to Islamic State and Al Qaeda, which are seeking to expand their reach into coastal countries from the central Sahel region, which includes Niger, Mali and Burkina Faso.

(Reporting by Bate Felix and Boureima Balima; Writing by Alessandra Prentice; Editing by David Holmes)