The United Nations is seeking 2,500 extra troops and police to shore up its peacekeeping operations in Mali, one of its most dangerous missions worldwide.

UN spokesman Stephane Dujarric said Thursday the MINUSMA mission also needs more air assets and quick-reaction forces after a series of attacks that left 12 peacekeepers dead in May alone.

"It's clear to everyone that the security situation in parts of Mali is deteriorating. UN staff have paid for it in blood," Dujarric said.

Secretary-General Ban Ki-moon has proposed adding 2,049 troops and 480 police to MINUSMA, which currently has about 12,000 personnel.

The Security Council is due to consider steps to strengthen MINUSMA, with a vote on extending the mandate of the mission set for June 29.

Two attacks on Tuesday in the northern city of Gao killed a Chinese peacekeeper and three civilians including a French contractor. Both were claimed by Al-Qaeda in the Islamic Maghreb (AQIM).

The deaths bring to 12 the number of peacekeepers killed in Mali in May alone, according to the UN.

"We are talking about quick-reaction forces, air assets, additional troops specialized in high security convoys," said Dujarric.

Deployed in July 2013, MINUSMA is already making use of drones and other technology to protect its bases.

In a report to the council this week, Ban said the mission needs an attack helicopter unit, armored personnel carriers and transport helicopters.

He also stressed the need to improve intelligence-gathering.

The request for more troops includes a 650-strong quick reaction force, an aviation unit of 85 personnel and the deployment of special forces in Timbuktu and Kidal for intelligence and surveillance.

A special team of 30 officers would be based in Bamako to support crisis response.

AQIM has claimed responsibility for two attacks in Bamako in the past 15 months: the March 2015 attack on a bar that left five dead and the November assault on the Radisson Blu hotel that killed 20 people including 14 foreigners.