Image copyright AP Image caption Mr Dipon is the latest victim of suspected Islamists

A Bangladeshi publisher of secular books has been hacked to death in the capital Dhaka in the second attack of its kind on Saturday, police say.

Faisal Arefin Dipon, 43, was killed at his office in the city centre, hours after another publisher and two secular writers were injured in an attack.

A local affiliate of al-Qaeda said it carried out the attacks.

There has been a series of attacks on secularists since blogger Avijit Roy was hacked to death in February.

Both publishers targeted on Saturday published Roy's work.

Mr Dipon was found dead at the Jagriti Prokashoni publishing house, in his third-floor office.

"I saw him lying upside down and in a massive pool of blood. They slaughtered his neck. He is dead," his father, the writer Abul Kashem Fazlul Haq, said, quoted by AFP.

Earlier on Saturday, armed men burst into the offices of publisher Ahmedur Rashid Tutul.

Image copyright AP Image caption Mr Dipon's father said he saw him lying in a pool of blood

Image copyright AP Image caption The publisher's death triggered protests

Image copyright EPA Image caption Ranadeep Basu was one of three men injured in an attack earlier on Saturday

They stabbed Mr Tutul and two writers who were with him, locked them in an office and fled the scene, police said.

The three men were rushed to hospital, and at least one of them is in a critical condition.

The two writers were named by police as Ranadeep Basu and Tareque Rahim.

Ansar al-Islam, al-Qaeda's Bangladeshi affiliate, posted messages online saying it had carried out Saturday's attacks.

Roy, a US citizen of Bangladeshi origin and critic of radical Islamism, was murdered in February by suspected Islamists. His wife and fellow blogger Bonya Ahmed was badly injured in the attack.

Three other bloggers have since been killed.

Timeline: Attacks on bloggers