* Grenade thrown at police post in Garissa
* No casualties reported
* Islamist al Shabaab militants suspected (Adds quotes, details)
By Noor Ali-Isiolo
GARISSA, Kenya, Oct 1 (Reuters) - Suspected al Shabaab militants threw a hand grenade at a Kenyan police post on Monday in the northern town of Garissa close to the border with Somalia, police said, a day after two police officers were shot dead in the same town.
Kenya has been rocked by a series of grenade and gun attacks since it sent troops into Somalia last October in pursuit of Islamist al Shabaab rebels whom it blamed for kidnapping its security personnel and Western tourists.
"A hand grenade was thrown, it dropped and exploded but nobody was injured," Garissa county commissioner Mohamed Maalim said, adding a gunfight ensued for about 10 minutes.
"The police fought back, secured the post and repulsed the gang," he said.
Maalim said police suspected it was an al Shabaab attack, the third in two days, which follows the killing of two policemen in Garissa and a separate bombing in which three children attending a Sunday school were hurt when militants threw a hand grenade at a church in Nairobi.
The attacks on Kenyan soil have intensified since Kenyan troops, alongside other African Union forces, launched an offensive against the southern Somali port of Kismayu, al Shabaab's last stronghold, forcing the rebels to flee.
"This is a heinous act by al Shabaab. They are out to cause chaos out of bitterness from their losses in Somalia," Maalim said. Security sources said police and paramilitary forces were searching for the gunmen.
Most of the inhabitants of Garissa are ethnic Somalis. The town is 180 km (110 miles) from Kenya's border with Somalia.
In July masked assailants launched simultaneous gun and grenade raids on two churches in Garissa, killing at least 17 people in the worst attack in the country since Kenya sent troops into Somalia.
Local residents say tension is running high after the latest attack on police.
"Security officers are going from house to house, breaking into homes and roughing people up," said Mohammed Gabow, former Mayor of Garissa, who is now an elected civic leader in Bulla Iftin, where the police post is located. (Additional reporting by Abdisalan Ahmed; Writing By Drazen Jorgic; Editing by Michael Roddy)