At least four Kenyan government workers are dead after their vehicle was hit by a rocket-propelled grenade in northeastern Kenya.

Police say the vehicle was carrying eight education and security officials when it was attacked Thursday in the El Wak area, not far from the Kenyan-Somali border.

It was not immediately clear who was behind the attack.

The incident is the latest in a series of attacks across the country, following the Kenyan army's incursion into Somalia to pursue al-Shabab insurgents, who Kenya blames for several cross-border kidnappings of foreigners.

On Wednesday, a Kenyan man who admitted to being a member of al-Shabab, pleaded guilty to one of two grenade attacks that took place in Nairobi earlier this week. The explosions killed one person and injured more than 20 others.

Al-Shabab has warned it will carry out attacks inside Kenya in response to the Kenyan army offensive.

The prime minister of Somalia's transitional government says he supports Kenya's military operation, despite earlier comments by Somalia's president casting doubt on the government's support for the move.

On Monday, President Sheikh Sharif Sheikh Ahmed said his government opposes Kenyan military action in Somalia, and that only African Union troops can operate legally in the country.

Somali Prime Minister Abdiweli Mohamed Ali told VOA Wednesday that Kenyan forces can, in his words, “stay as long as they want to.”

Mr. Ali said Somalia and Kenya have a common strategy, purpose and desire to defeat al-Shabab.