The European Union voiced its concern Wednesday over the political turmoil convulsing Turkey as the government conducted a new mass purge of senior police officers.

In its strongest comments yet on the widening corruption scandal engulfing Prime Minister Recep Tayyip Erdogan, the EU called for Turkish authorities to ensure they acted impartially.

The turmoil has rocked Erdogan's government to its very core just weeks before crucial local elections in March and has sent Turkish financial markets tumbling.

In the latest development, 16 police chiefs in several major cities including Ankara, Izmir, Antalya and Diyarbakir as well as the deputy head of national security, were fired Wednesday under a decree signed by Interior Minister Efkan Ala.

The latest purge came just a day after the government fired 350 police officers in the capital Ankara -- bringing the total number sacked to over 700 since mid-December when the graft scandal broke, according to local media tallies.

News reports said Tuesday that another 25 people had been detained on suspicion of bribery and fraud in the widening corruption probe that has targeted several key Erdogan allies.

One of the main prosecutors in the probe, Zekeriya Oz, has also been reassigned following media reports over alleged corruption.

"Turkey is going through one of the deepest crisis in its history. If the allegations are true, it means that the government is rotten to the core," wrote Mehmet Tezkan, a columnist with the liberal Milliyet newspaper.

The executive of the EU -- which Turkey has long aspired to join -- said the crisis was a "cause of concern".

"We urge Turkey, as a candidate country committed to the political criteria of accession, including the application of the rule of law, to take all the necessary measures to ensure that allegations of wrongdoing are addressed without discrimination or preference in a transparent and impartial manner," it said in a statement.

The government insisted it would overcome the crisis.

"The government is in charge. We will never let the political and economic stability of Turkey be disturbed," Deputy Prime Minister Ali Babacan said.

Battling to contain the biggest threat to his 11 years in power, Erdogan has branded the investigation a "dirty" plot to try to topple his Islamic-rooted government.

He and his allies have blamed supporters of a powerful Muslim cleric who lives in exile in the United States but wields considerable influence in Turkey's judiciary and police.

The crisis erupted in December when dozens of leading businessmen and political figures -- including the sons of three ministers -- were detained.

Erdogan was forced into a major cabinet reshuffle after the three ministers concerned resigned and the government has since gone on the offensive to root out foes in the police and judiciary.

Erdogan's critics accuse him of desperately trying to protect cronies caught up in the investigation which has focused on alleged bribery in construction projects and illicit money transfers by a state-owned bank to sanctions-hit Iran.

Media reports have said Erdogan's son was also set to be rounded up last month but the prosecutor involved was subsquently removed.

"There are some allegations about the sons of ministers. The court is dealing with this. If there are unlawful actions, corruption or bribery, this will eventually be revealed. But we cannot take allegations as fact," AKP spokesman Huseyin Celik told reporters.

In a new twist to the increasingly complex powerplay, the top judicial body the Supreme Board of Judges and Prosecutors (HSYK) said Tuesday it would investigate allegations that the new Istanbul police chief was blocking prosecutors from carrying out further arrests, as well as alleged misconduct by prosecutors.

Erdogan has vowed to battle what he terms "a state within a state" -- an apparent reference to followers of influential cleric Fethullah Gulen.

The so-called Gulenists -- once staunch supporters of Erdogan's Justice and Development Party (AKP) -- hold key positions in various government branches including the police and judiciary.

The crisis has called into question the political future of the prime minister, arguably one of the most powerful figures in modern Turkey who took office after years of government instability and an economic meltdown.

In his campaign against the Gulenists, he is now seeking to mend fences with the once all-powerful army that he had fought hard to rein in.

He has said he is willing to see fresh trials for hundreds of military officers jailed in 2012 and 2013 for allegedly plotting coups against his government.

Gulen's followers were key backers of the AKP when it took office but tensions emerged over last year's massive street protests and government plans to shut down a network of private schools run by the movement.

Turkey's financial markets remain jittery, with the Istanbul stock market down slightly while the dollar was at around 2.17 compared to its all time low of 2.19 on Monday.