Heavy rain is slowing Kenyan forces trying to advance on a town in southern Somalia held by militant group al-Shabab.

Kenyan troops were positioned near the rebel-held town of Afmadow on Tuesday, as al-Shabab rushed reinforcements to the city. A Somali journalist tells VOA that the rain has prevented the troops from moving forward.

Meanwhile, Kenya’s Defense Minister Mohammed Yusuf Haji and Foreign Minister Moses Wetangula have arrived in the Somali capital, Mogadishu, for talks with government officials.

Kenya sent troops across the border into Somalia over the weekend, in what it called a “pursuit operation” against al-Qaida-linked al-Shabab.

Kenyan officials blame al-Shabab for the death of one tourist and the kidnapping of four others on Kenyan territory.

Al-Shabab has denied responsibility for the abductions, and warned Monday that it would attack targets in Kenya unless the government withdraws its troops from Somali territory.

The kidnapping victims include a British tourist, a French woman and two Spanish aid workers.

Meanwhile, Kenyan police said Tuesday they arrested two British citizens suspected of trying to join al-Shabab.

The exact size and location of Kenyan forces in Somalia is not clear. Residents have reported seeing columns of 30 to 40 armored vehicles.

Al-Shabab is calling on all Somalis to defend against what it calls “the enemy.” Witnesses said Monday that convoys of al-Shabab fighters had left the rebel-controlled port city of Kismayo to confront the Kenyan forces.

The last country to invade Somalia was Ethiopia, which deployed troops in 2006 to oust Islamist militants who had briefly taken over the capital. Al-Shabab emerged as the main group fighting the Ethiopians, who withdrew at the beginning of 2009.