"We have solved the July 11 bombings case. The whole attack was planned by Pakistan's ISI and carried out by Lashkar-e-Taiba and their operatives in India," AN Roy, Mumbai's police chief, told a news conference.

ISI or the Inter-Services Intelligence agency is Pakistan's military spy agency.

The announcement came a day after Mumbai police said they had arrested four more people in connection with the attacks on rush-hour commuter trains and stations that killed 186 people and wounded hundreds.

The new arrests took the total number of people in custody for their alleged role in the blasts to more than 15.

They include an engineer, a journalist, a computer software professional and a doctor.

Seven blasts ripped through commuter trains and platforms in India's financial hub and home of Bollywood cinema.

In the immediate aftermath, Indian security officials blamed local Muslims with links to Pakistan, and named Lashkar-e-Taiba as a prime suspect.

The Pakistani government and Lashkar have denied any role in the attacks and Islamabad offered to help with investigations.

Pakistan said India shouldn't point fingers without evidence, after Mumbai police on Saturday blamed Pakistani spies and militants for a series of blasts that killed 186 people in Mumbai on July 11.

"It is baseless, it is irresponsible and (done) out of habit," Tasnim Aslam, Pakistan's Foreign Ministry spokeswoman said, adding that an official statement would be released later.

Tariq Azim Khan, Minister of State for Information, also harked on what he called India's knee-jerk reaction in blaming Pakistan for militant acts when there are several groups running insurgencies there.

"India has always chosen this path of pointing fingers at Pakistan without evidence," he said. "If they have any evidence, they should provide us evidence and we will carry out our investigations."