Gunmen have attacked a hotel used by westerners in Ouagadougou, the capital of Burkina Faso, taking hostages and reportedly killing at least 20 people.

Eyewitnesses said two car bombs went off outside the Splendid hotel at around 19:30 local time (same as GMT).

Three to four masked men then stormed the Splendid Hotel, which is used by UN staff and westerners, witnesses said.

Robert Sangare, a hospital director in the city, said at least 20 people had died and 15 more wounded.

French ambassador Gilles Thibault tweeted that an operation to free hostages from the hotel was under way, and witnesses said part of the hotel was on fire.

Foreign Minister Alpha Barry had earlier said he would not rule out the co-operation of French troops.

One group that monitors jihadist networks said al-Qaeda in the Islamic Maghreb claimed it was behind the attack.

Witnesses said the gunmen had initially entered the Cappuccino cafe near the hotel. One employee at the cafe told Agence France Presse that "several people" had been killed there.

Eyewitnesses reported hearing exchanges of gunfire between the men and security forces, as well as sporadic gunfire from inside the four-star hotel, which is close to the country's international airport.