Malian President Ibrahim Boubacar Keita cut short a trip to a regional summit in Chad to return to Bamako, his office said. French President Francois Hollande said France would “use all the means available to us on the ground to free the hostages”.
The raid on the hotel, which lies just west of the city centre near government ministries and diplomatic offices, comes a week after Islamic State militants killed 129 people in Paris.
The identity of the Bamako gunmen, or the group to which they belong, is not known.
Northern Mali was occupied by Islamist fighters, some with links to al Qaeda, for most of 2012. They were driven out by a French-led military operation, but sporadic violence has continued in Mali’s central belt on the southern reaches of the Sahara, and in Bamako.
One security source said as many as 10 gunmen had stormed the building, although the company that runs the hotel, Rezidor Group, said it understood that there were only two attackers.
The hotel’s head of security, Seydou Dembele, said two private security guards had been shot in the legs in the early stages of the assault.
“We saw two of the attackers. One was wearing a balaclava. The other was black-skinned. They forced the first barrier,” Dembele told Reuters.
Within minutes of the assault, police and then soldiers had surrounded the hotel and were blocking roads leading into the neighbourhood.
It is not the first time Bamako has come under attack.
An Islamist group claimed responsibility for the death of five people last March in an attack on a restaurant in Bamako that is popular with foreigners.
And in August, 17 people were killed during an attack on a hotel in Sevare in central Mali, some 600 km (375 miles) northeast of Bamako that was claimed by the Sahara-based Islamist militant group al-Mourabitoun.
The dead in Sevare included nine civilians, five of whom worked for the U.N. mission in Mali (MINUSMA), as well as four Malian soldiers and four militants.
In the wake of last week’s Paris attacks, an Islamic State militant in Syria told Reuters the organisation viewed France’s military intervention in Mali as another reason to attack France and French interests.
“This is just the beginning. We also haven’t forgotten what happened in Mali,” said the non-Syrian fighter, who was contacted online by Reuters.
“The bitterness from Mali, the arrogance of the French, will not be forgotten at all.”
France said it was despatching 50 elite counter-terrorism officers to Bamako imminently.
Reuters