Mumbai, Jan 23 (IANS): Hours after the Mumbai police claimed to have arrested two key suspects in the July 13, 2011 serial blasts that killed 27 people, the union home ministry Monday expressed dismay over the claims, noting that one of the two held was an informer for the Delhi Police and the Intelligence Bureau.

The Anti Terrorism Squad (ATS) of Mumbai police has also sought the custody of another suspect, held in a separate fake currency case, for the Mumbai terror attack probe.

"Naqi Ahmed Vasi Ahmed Sheikh, 22, and Nadeem Akhtar Ashfaque Sheikh, 23, have been arrested from different areas of south-central Mumbai in connection with the case," ATS chief Rakesh Maria told reporters in Mumbai.

In New Delhi, home ministry officials, unwilling to be named, countered the ATS claim, clearly demonstrating that there had been no coordination among security agencies probing terror cases.

"We are baffled at the arrest of the 22-year-old Naqi Ahmed Vasi Ahmed Sheikh, who has in fact been helping Delhi Police special cell and the Intelligence Bureau. He was the person who provided crucial leads to Waqas and Tabrez, the two bombers in the 13/7 blast," the officials said.

"Naqi Ahmed was in Mumbai to help track down the two bombers. It was a highly secret operation monitored by the nation's security top brass from the capital," they added.

Claiming to have cracked the serial blasts that rocked Zaveri Bazar, Opera House and Dadar in south and central Mumbai in July last year, Maria said the third suspect Haroon Rashid Naik, 33, was already behind bars in Mumbai.

"So, there would be technically three arrests and three (accused still) wanted in the case so far," he said.

"Naqi is originally a resident of Darbhanga in Bihar, but had been in Mumbai since September-October 2010. Nadeem is from Deora Bandhauli, also in Darbhanga district, and has been staying in Mumbai since around the same time," Maria said.

Maria said the main accused in the case, Yasin Bhatkal alias Imran, was still untraced. Bhatkal is known to be a prime operative of the Indian Mujahideen terror group.

"Yasin Bhatkal is the main accused in this case. He started the Darbhanga (terror) module where he held programmes to indoctrinate young boys and used them in such blasts," Maria said.

Ahead of the serial blasts, Bhatkal had give Nadeem a cloth packet, containing the explosives and detonators, to hand it over to Naqi. Naqi passed on the packet to another suspect, the police officer said.

Bhatkal gave Naqi Rs.1.5 lakh to assist in the execution of the serial blasts, he said.

Naqi, whose association with Bhatkal dates back to 2008, also conducted a recce of the blast sites, he said.

The investigation was being conducted by teams of Mumbai police, Maharashtra's criminal investigation department, the National Investigation Agency and others, with support from security agencies in many states, he said.

Three blasts at close intervals July 13 last year shook the country's diamond and gold hubs - Opera House and Zaveri Bazar - and a busy commercial area of Dadar, killing at least 27 people and leaving around 125 injured.