Eighteen soldiers and a civilian were killed in a car bomb attack on a military base in Niger on Thursday, the interior minister said, adding that one of the assailants had taken several trainee officers hostage.

"We have 19 dead in Agadez, 18 soldiers and a civilian," Abdou Labo said at a press conference, adding that four suicide bombers were killed in the blast, one of two attacks in Niger on Thursday. "A fifth bomber has locked himself up in an office with several trainee officers as hostages."

Twin car bombings at an army base and a French-run uranium mine in northern Niger killed at least 10 people Thursday, in unprecedented attacks claimed by an Islamist group fighting French-led troops in neighboring Mali.

The Movement for Oneness and Jihad in West Africa (MUJAO) claimed the bombings, calling them punishment for Niger's participation in a French-led military offensive against Islamist extremists who had seized control of northern Mali last year and ruled it under a brutal version of Islamic law for some 10 months.

An Algerian court sentenced 14 Malian members of the National Movement for the Liberation of Azawad (MNLA) to 20 years' jail for arms smuggling and entering the country illegally, El Khabar daily reported Monday.

The Malians, who were sentenced on Sunday by the criminal court in the southern town of Ouargla, were accused of entering Algeria illegally with a shipment of weapons from Libya, the Arabic-language daily said.

A Nigerian warplane crashed in Niger on Monday, from where it was conducting military operations in neighboring Mali, and the two pilots were killed, Nigeria's army said in a statement.

The fighter jet was part of Nigeria's air fleet engaged with an African force battling hardline Islamists in Mali. An army source in Niamey said it had suffered a "mechanical" problem.

U.S. Secretary of State John Kerry met French President Francois Hollande in Paris on Wednesday to discuss the crisis in Mali on the third leg of a European tour so far dominated by the Syrian conflict.

Kerry, who has hailed France's "successful" mission in Mali, will also hold talks with French Foreign Minister Laurent Fabius and address a joint press conference in the afternoon.

U.S. President Barack Obama sent 40 additional soldiers to Niger to help with intelligence efforts as French and African troops battle an Islamist insurgency in neighboring Mali, the White House said in a letter to Congress Friday.

The U.S. troops join another 60 or so already in the West African country, and are tasked with providing "support for intelligence collection and will also facilitate intelligence sharing with French forces conducting operations in Mali, and with other partners in the region," the president said.

Malian troops were battling armed Islamists in the northern city of Gao on Thursday in clashes that left the main courthouse in flames, an Agence France Presse correspondent and a military source said.

Fighting had first erupted overnight in Gao, where a military official and witnesses reported heavy gunfire around two main entrances to the main city in the north of the country.

Three people were killed when their light plane crashed at Niamey airport, Niger's ministry of transport has announced in a statement.

In the accident on Monday afternoon, "the three people on board, all of Nigerien nationality, lost their lives," the ministry said in the statement read on public television on Monday night.

Islamist fighters have dynamited a strategic bridge near the Niger border on the road to Gao, one of the main towns in northern Mali occupied by extremists, sources said Friday.

"The Islamists dynamited the Tassiga bridge. No one can pass to Niger or come to Gao," said the owner of a transport business, Abdou Maiga.

The conflict in Mali has caused nearly 150,000 people to flee the country, while about another 230,000 are internally displaced, the U.N. humanitarian agency said Tuesday.

According to OCHA, the U.N. High Commissioner for Refugees has registered 144,500 refugees in neighboring countries -- 54,100 in Mauritania, 50,000 in Niger, 38,800 in Burkina Faso and 1,500 in Algeria.