LAHORE, Pakistan (Reuters) - Police have opened criminal cases against nearly 17,000 members of Pakistan’s outgoing ruling party over breaking election rules, a statement said on Monday, as the country prepares to go to the polls next week.

FILE PHOTO: Supporters of the Pakistan Muslim League - Nawaz (PML-N) chant march towards the airport to welcome ousted Prime Minister Nawaz Sharif and his daughter Maryam, in Lahore, Pakistan July 13, 2018. REUTERS/Mohsin Raza/File Photo

The latest 16,868 cases, which the police statement said were registered in the eastern province of Punjab over the past four days, come after the party said police had also detained hundreds of members of the Pakistan Muslim League-Nawaz (PML-N) in the central city of Lahore.

The statement gave no details of which election rules were suspected of having been broken.

The party’s founder, ousted former prime minister Nawaz Sharif, facing a conviction in absentia on corruption charges, was jailed last week when he returned to the country seeking to revitalize the PML-N ahead of the July 25 vote.

The campaign has been riven by that accusations Pakistan’s powerful military is working behind the scenes to skew the contest in favor of ex-cricket hero Imran Khan.

The military, which has ruled the nuclear-armed country for almost half its history and ended Sharif’s second stint in power in 1999 in a bloodless coup, has repeatedly denied any interference. Khan has also denied colluding with the military.

National polls indicate a close race between the PML-N and the Pakistan Tehreek-e-Insaf (PTI, or Pakistan Justice Movement) led by Khan, with the Pakistan Peoples Party in third place.

Cases were also registered against 39 members from Khan’s movement, the police statement said.

It said 270 people had been detained, but it did not say which political party they belonged to.

The independent Human Rights Commission of Pakistan said it was concerned about the legitimacy of the election, saying “the public perception that all parties have not been given equal freedom to run their election campaigns”.

Police detained the members of the PML-N in Lahore last week ahead of a rally by tens of thousands of supporters welcoming home Sharif, who was arrested upon landing.

Three local government leaders of the PML-N said the crackdown involved intimidation and threats by the police, intelligence agencies and a paramilitary force to keep them from attending the rally welcoming Sharif.

They spoke to Reuters on condition of anonymity fearing a backlash from authorities.

On Sunday, Pakistani authorities opened a criminal investigation into leaders of PML-N under an anti-terrorism law.

The case relates to a march staged by the PML-N on July 13, when Sharif returned to Pakistan, which defied a ban on holding public rallies.