Image copyright AFP Image caption Security has been stepped up since the wave of attacks began

Bangladesh's Prime Minister Sheikh Hasina has vowed to bring an end to a wave of targeted killings of minorities and secular citizens in the country.

She said her government would do whatever it took to stop the attacks.

Her comments came a day after police launched a concerted drive against Islamists, arresting more than 3,000 people.

The opposition has accused the government of using the operation to target political opponents.

Who is behind the Bangladesh killings?

Is extremism on the rise in Bangladesh?

Lurching from secularism to sectarian terror?

'Opposition activists held'

"It may take time, but God willing, we will be able to bring [the perpetrators] under control," Ms Hasina said at a meeting of her ruling Awami League party on Saturday.

"Where will the criminals hide? Each and every killer will be brought to book," she added.

Police launched the week-long campaign on Friday, saying they were focused on arresting Islamist militants.

However, critics say many ordinary criminals were among those held.

Image copyright AFP Image caption Regular protests have been held following the attacks on secular bloggers and minorities

Meanwhile, Fakhrul Islam Alamgir, the leader of the opposition Bangladesh Nationalist Party said that "hundreds of opposition activists have been arrested in the police drive".

"In the name of the crackdown against Islamist militants, many ordinary and innocent people are being detained," he told the AFP news agency.

The Bangladeshi government denied targeting opposition activists.

"During a major operation you don't take chances, you do make a lot of arrests and then after the arrests are made you screen them," Nadeem Qadir, a government spokesman at the Bangladesh High Commission in London, told the BBC.

"There's no targeted political elements in this case, it's an operation...to stop this targeted killing, it's as simple as that."

About 40 people, including secular bloggers, academics, gay rights activists and members of religious minorities, have been killed in attacks in the past few years.

On Friday, a Hindu monastery worker was hacked to death in Pabna district.

In the past week, a Hindu priest, a Christian grocer and the wife of an anti-terror police officer were all killed in attacks by suspected Islamist militants.

Analysts say the killing of a police officer's wife last Sunday may have triggered the crackdown.

Who is being targeted?

Secular bloggers, academics, gay rights activists, and members of religious minorities including Shia, Sufi and Ahmadi Muslims, Christians and Hindus have all been killed, many of them hacked to death.

A university professor whose family said he was not an atheist was murdered in April, suggesting the list of those at risk had widened further.

Who exactly is behind the attacks remains unclear. Bangladesh has myriad extremist groups and there have been few convictions over the attacks.

Many of the attacks have been claimed by so-called Islamic State (IS) or al-Qaeda-linked groups.

However, the government has disputed these claims, with some members blaming opposition parties and local Islamist groups. Bangladesh's home minister has suggested an Israeli link to the killings, describing an "international conspiracy" against Bangladesh.

Both the opposition and the Israeli government have denied any involvement - and Israel described the accusations as "utter drivel".

Until the killings stop the government itself will face accusations of not doing enough to protect minorities in the Sunni-dominated nation.