Kenyan authorities say more than 650 people have been arrested since the Kenyan government ordered all refugees living in urban areas to return to their camps a week ago in a bid to end attacks.

The announcement on Tuesday came a day after six people were killed in bomb attacks in the capital Nairobi and a week after a deadly attack on a church in the port city of Mombasa.

The majority of those arrested were rounded up for staying in Kenya without the proper documentation, the office of the Kenyan internal security minister told Al Jazeera.

Of the 657 people arrested, 200 were being questioned on suspicion of links to terrorist attacks or terrorism, the inspector general of police said.

Kenyan security officials believe armed groups have used refugee camps as bases to prepare attacks and then mingled with residents in urban areas to carry them out.

The country's interior minister condemned Monday's triple blasts in the capital.

"This act of cowardice perpetrated against innocent and peace-loving Kenyans who were going about their normal activities is barbaric," Joseph Ole Lenku said in a statement.

The blasts targeted two small restaurants and a local clinic in a particularly densely populated area of Eastleigh, an area often known as "Little Mogadishu" because of its predominantly Somali population.

No one has claimed responsibility for the blasts.

Kenyan police regularly arrest scores of people after similar attacks in sweeping security operations, but later release most after questioning.

Church attack

Al Jazeera's Tania Page, reporting from Nairobi, said the city had grown more tense in the last week after the government ordered all refugees, most of whom are Somali, to leave urban areas and head to two designated refugee camps.

The order followed the deaths of six people as assailants opened fire on a church service in Mombasa on March 23.

"The government says that's because some of the people responsible for recent attacks have been refugees," our correspondent said.

"The people of Eastleigh argue they are suffering collective punishment for the actions of a few," she added.

Kenya has been hit by a series of attacks since sending troops into southern Somalia in October 2011 to battle al-Qaeda-linked al-Shabab rebel group.

The armed group claimed responsibility for the most deadly attack, in which they laid siege to Nairobi's upmarket shopping mall Westgate in September, killing at least 67.