Niger closed an oil pipeline used to export crude through a port in neighboring Benin, ratcheting up tensions between the two countries amid an ongoing border impasse.

Landlocked Niger has turned off the valves on the 1,200-mile (1,930-kilometer) conduit from the Agadem oil field operated by China National Petroleum Corp., Oil Minister Mahaman Moustapha Barké Bako said Thursday. The pipeline — built by CNPC as part of a $4.6 billion investment in Niger’s petroleum industry — ferries crude to the Sèmè Kpodji pipeline terminal in Benin for export.

The blocked shipments are part of a $400 million commodity-backed loan from CNPC. Niger, which borrowed the funds from China at 7% interest, plans to repay the debt by shipping oil to the Asian nation for 12 months.

A dispute erupted between the two countries last month, when Benin barred oil exports from its port after junta-led Niger refused to open its land border to goods coming from its southern neighbor. The Economic Community of West African States, a regional bloc, closed Niger’s land and air borders last year to convince the military government to restore civilian rule and despite lifting the sanctions earlier this year, Niger has kept its border shut.

Last week, five Nigerien nationals who traveled to the Cotonou port were arrested by Benin after allegedly failing to properly identify themselves. On Thursday, a Benin court ordered the continued detention of three of the oil workers for trial, including the deputy general manager of the West African Pipeline Co., the local affiliate of CNPC.

“We cannot stand by while our oil is stolen by other people because we are not present where it is being loaded,” Bako said during a visit to Agadem. “No matter the price or how long it lasts, as long as Benin and WAPCO don’t let Niger attend the loading of our crude, we cannot reopen this tap.”

CNPC didn’t respond to a request for comment sent by email.