About 2,500 people have marched in Kenya's Garissa town in a show of defiance against militant Islamist group al-Shabab following its deadly assault on a local university.

Muslims and Christians took part in the march, vowing to remain united against the al-Qaeda-linked militants, says a BBC reporter in Garissa.

Students also protested in the capital, demanding greater security on campuses.

The assault on Garissa University on Thursday killed 148 people.

It was the deadliest attack by al-Shabab in Kenya.

'Mercy'

The BBC's Bashkash Jugsooda'ay reports from Garissa in north-eastern Kenya that protesters promised to co-operate with the security forces to flush out militants in their community.

However, they were also critical of the security forces, saying they were slow in their response to the assault.

Al-Shabab says it is at war with Kenya

Many families are still waiting to identify loved ones killed in the assault

Four gunmen stormed the campus, taking students hostage in dormitories and killing them.

The government says the security forces responded swiftly, and saved the lives of many other students.

The security forces also came under heavy criticism at the protest in Nairobi, organised by students from the city's main university.

Protesters said they were no longer prepared to be "at the mercy of al-Shabab" and demanded that the government tighten security at universities and schools across Kenya.

A candle-lit vigil is due to be held later in the capital to end three days of national mourning.