New Delhi  - India's western state of Gujarat was on high alert Tuesday after police found nine bombs in Surat city, three days after synchronized blasts killed up to 50 people in the state's main city of Ahmedabad.

Police defused all nine bombs, which were found in residential areas, in markets and along roads in the Varachha area of Surat, which is among the world's biggest diamond-polishing centres and is located 200 kilometres south of Ahmedabad.

"Most of these were crude bombs and have been sent to the forensic lab for analysis," Inspector P Mangabe at the Surat police control room said by telephone.

In all, 12 bombs have been found in the city since Sunday, and police asked people to stay indoors and for schools and educational institutions in the Varachha area to close down immediately.

"Almost all major cities - including Ahmedabad, Surat, Vadodara and Rajkot - are on high alert, and search and combing operations are on to find if there are more explosive devices at public places," Mangabe said.

In a related development, three bombs were defused near Jodhpur in neighbouring Rajasthan state, where blasts claimed 65 lives in May, the NDTV network reported.

On Saturday, 16 bombs ripped through markets, residential areas, public transport and hospitals in Ahmedabad. Local media reported that the explosions claimed 50 lives and wounded 159, but the Ahmedabad police has confirmed only 43 deaths so far.

A little-known Muslim militant group called the Indian Mujahedin claimed responsibility for the bombings and warned of more attacks against Hindus.

In an e-mail sent minutes before the blasts, the group said the attacks were revenge for the 2002 Hindu-Muslim riots in Gujarat, in which 1,000 people, mostly Muslims, were killed.

In Ahmedabad, senior police officials told the PTI news agency that investigators had obtained leads in the case.

The police also prepared a sketch of a suspect who was seen planting an explosive in Surat.

"We have got some leads, and we are working on them, but we will not reveal it to the media at present," an official was quoted by PTI as saying.

Meanwhile, in India's financial capital of Mumbai, police detained three Kashmiri youth for questioning in connection with the Ahmedabad bombings.

Detailed maps of Ahmedabad were found on the trio, who claimed they had come to Mumbai looking for jobs, police said. (dpa)