One person has died and at least 30 others have been injured by a series of small bombs planted in the southern Pakistan city of Karachi.

The six devices went off within an hour of each other on Monday evening in different locations of the port city in Sindh province.

A provincial police officer said bomb disposal teams had been sent to determine the nature of the devices.

The explosions come a day after a suicide bomber killed at least 18 people, including police officers who were securing a rally to mourn those who had died a year earlier in the Red Mosque (Lal Masjid) raid in Islamabad.

Al Jazeera's Kamal Hyder said that the devices used on Monday were "amateur" and had been planted in Pashtun dominated areas.

Babar Khattak, the provincial police chief, said the 150g-200g bombs may have been intended to provoke ethnic unrest.

"It seems the series of blasts was carried out to create harassment and fear among the citizens," he said.

The bombs had been hidden in motorcycles, bicycles and auto-rickshaws.

The police said five men had been detained. There has been no claim of responsibility.