Photo: The Canadian Press. All rights reserved.

In this picture dated Sunday, Jan. 13, 2013 and released by the French Army Communications Audiovisual office (ECPAD), a French soldier of the 2nd Marine Infantry Regiment based in Le Mans, western France, prepares ammunition before distribution at Bamako airport, Mali. An official at France's Defense Ministry says the country will "gradually deploy" a total of 2,500 troops to Mali, and the French president says the military operation will last until security has been restored and African forces are ready to take charge. (AP Photo/Arnaud Roine, ECPAD)

French troops pressed north in Mali toward territory occupied by radical Islamists on Wednesday, launching a land assault which will put soldiers in direct combat "in 1 to 72 hours," military officials said.

French ground operations began overnight, France's military chief of staff Adm. Edouard Guillaud, said on Europe 1 television Wednesday. He stressed that French infantry units "will be fighting directly in coming hours, but I am unable to say whether it is in one hour or in 72 hours. ... Of course, we will be fighting directly."

Armoured vehicles loaded with French troops were seen heading toward Niono. The natural target for the French infantry is Diabaly, located 400 kilometres (250 miles) northeast of the capital and roughly 70 kilometres (45 miles) north of Niono. French warplanes have carried out airstrikes on Diabaly since the weekend, when a column of dozens of rebel vehicles cut off the road to Diabaly and seized the town as well as its military camp.

A trickle of refugees left on foot from Diabaly, a town seized two days ago by the jihadists who have held onto it despite a punishing bombing campaign by French fighter jets. The refugees arrived in Niono town, 70 kilometres (43 miles) south of Diabaly, according to residents.

Ibrahim Komnotogo, a resident of Diabaly who heads a USAID-financed rice agriculture project, happened to be outside the town when the jihadists encircled it. He has 20 employees and contractors who he says are stuck inside the town, which has a population of 35,000. He told The Associated Press that al-Qaida-linked rebels have sealed off the roads and were preventing people from leaving. He was last able to speak to his employees on Tuesday, and had not had news of them since, after the telephone network was cut.

Komnotogo says he fears the Islamists are planning to hide within Diabaly's mud-walled neighbourhoods and use the population as a human shield.

"The jihadists have split up. They don't move around in big groups ... they are out in the streets, in fours, and fives and sixes, and they are living inside the most populated neighbourhoods," he said, explaining that they had taken over the homes of people who managed to flee before the road was cut off.

French warplanes bombarded the military camp, but there have been no airstrikes inside the actual town, which begins at the eastern wall of the garrison. Residents have evacuated the neighbourhood called Bordeaux, after its sister city in France, which is only 500 metres (yards) from the camp, he said. They have moved mostly into a quarter called Berlin, about 1 kilometre (0.6 miles) from the military installation.

"They are preventing the population from leaving. We have been trying to get our employees out, but they can't leave," said Komnotogo. "They have parked their pickup trucks inside the courtyards of empty homes. They have beards. And they wear boubous (a flowing robe). No one approaches them. Everyone is afraid," he said.

French President Francois Hollande authorized the airstrikes last Friday after the Islamists began a push southward toward the capital from the northern half of Mali that they control. They seized the Afghanistan-sized north last April in the chaos following a coup in Mali's normally-stable capital.

Six days of airstrikes have done little to erode the Islamist gains in Mali, which some in the West fear could turn the region into a launching pad for terrorist attacks. The bombardments began in the town of Konna, which the rebels occupied last Thursday. After initially saying they had stopped the rebel advance, France's defence minister on Tuesday acknowledged that Konna was still in the hands of the rebels.