Dozens of Somalis were expelled from Kenya on Wednesday, officials said, as security forces maintained a major crackdown on suspected Islamists that has seen thousands rounded up in the capital.

Kenya's Interior Minister Joseph Ole Lenku said 3,000 people have so far been detained in the operation, and 82 of them flown back to Somalia's Mogadishu. He said hundreds more were still undergoing identity checks.

The two U.N. workers shot dead in central Somalia were working on the links between money transfer systems and piracy, the U.N. anti-drugs and crime agency said Wednesday.

Former British police officer Simon Davis, 57, and his French colleague, 28-year-old researcher Clement Gorrissen, were fatally shot by a man in uniform just after their arrival at the airport in Galkayo on Monday.

Kenyan security forces have rounded up thousands of Somalis or Kenyans of Somali origin, leaving many languishing in a football stadium, amid a major crackdown on suspected Islamists blamed for a string of attacks.

The operation, which local media say has involved more than 6,000 men from the police and from the elite General Service Unit, started on Friday and appeared to have been focused on Eastleigh, an ethnic Somali-dominated district of the Kenyan capital.

Two U.N. workers, a Briton and a Frenchman, were shot dead on Monday as they disembarked from a plane at an airport in Galkayo, central Somalia, officials and witnesses said.

United Nations sources confirmed the two men were international consultants with the U.N. Office on Drugs and Crime (UNODC). Britain's Foreign Office confirmed one was a Briton, and sources identified the second victim as a Frenchman.

Somali government forces fighting alongside African Union troops said they had taken back control of a key town Wednesday, driving Al-Qaida-linked Shebab rebels from a major central bastion.

El-Bur, some 350 kilometers (220 miles) northeast of the capital Mogadishu in the Galgadud region, is the latest town taken since the U.N.-backed AMISOM force launched a fresh offensive against the Shebab this month.

The United Nations warned Monday of an increased threat of attacks from Somalia's al-Qaida-linked Shebab as a major offensive launched against them this month gathers pace.

"Coinciding with the offensive and even ahead of it, Al-Shebab have become more active," U.N. envoy to Somalia, Nicholas Kay, told Agence France Presse.

Two people shot when attackers sprayed a Kenyan church with gunfire on Sunday have died of their wounds, taking the total killed in the attack to six, government officials said Monday.

The attack, in the Likoni district near the port city of Mombasa, came amid heightened warnings of a threat of Islamist violence in Kenya and despite boosted security in major cities.

Somali government forces supported by African Union troops took control of a key southern town on Saturday as they closed in on a major bastion of al-Qaida-linked Shebab rebels, officials and witnesses said.

Witnesses reported that the Somali and AMSIOM troops fought a heavy battle outside Qoryooley in lower Shabele region before finally wresting control of the town and closing on the Shebab coastal base of Barawe.

Somalia's Al-Qaida linked Shebab attacked a hotel crowded with army officers in a southern town days after African Union troops celebrated its capture from the Islamists, security officials said Tuesday.

A suicide bomber rammed a car packed full of explosives into the hotel, with gunmen then attacking, killing at least eight people, residents said.

Uganda warned Tuesday that Somalia's al-Qaida linked Shebab insurgents were planning to use fuel tankers as bombs, one day after Kenya thwarted a "massive" car bomb attack.

Both Uganda and Kenya are key contributors of troops to the African Union force fighting the Shebab in Somalia, and the Islamists have carried out major attacks in both countries in retaliation in the past.