French President Nicolas Sarkozy condemned Pakistan on Tuesday for allowing extremists 'safe havens' in its tribal border areas, as he paid tribute to the victims of the 2008 Mumbai attacks.

Mr Sarkozy, in Mumbai on the last day of a four-day visit to India, said it was 'unacceptable' that terror networks could find refuge in Pakistan and use it as a springboard to attack India, French troops in Afghanistan or other countries.

"It is unacceptable that India's security can be threatened by groups of terrorists acting from neighbouring countries," he said at the Oberoi hotel, one of the luxury hotels besieged by militants in November 2008.

"It is unacceptable for Afghanistan and for our troops that the Taliban and Al Qaeda find safe haven in the border regions of Pakistan. We know the price that the Pakistani people are paying for terrorism.

"But it is unacceptable for the world that terrorist acts should be masterminded and carried out by terrorist groups in Pakistan."

"I call on all Pakistani authorities to step up their efforts and show that they are resolute in combating these criminals," he added, vowing that 'there will be no limit to operational co-operation' in counter-terrorism with India.

Mr Sarkozy, accompanied by his wife Carla Bruni, earlier placed a wreath at a memorial in the south of the city for 18 police officers who lost their lives in the carnage.

The wave of attacks, which also targeted a Jewish centre, a popular tourist restaurant and the city's main railway station, killed 166 people in all, including two French nationals, and injured more than 300.

The deadly assault has been likened to those on the United States on September 11, 2001 and was blamed on the banned, Pakistan-based Islamist group Lashkar-e-Tayyaba (LeT), with help from elements in Pakistan's military.

Seven suspects of the Mumbai attacks have been put on trial in Pakistan, including alleged mastermind Zakiur Rehman Lakhvi, but none has been convicted.

In a 2009 cable from US secretary of state Hillary Clinton, released by WikiLeaks this week, she alleges that Lakhvi kept running the LeT even while in prison in Pakistan awaiting trial.

Sarkozy's comments on India's troubled neighbour mirror similar pronouncements made by US President Barack Obama and British Prime Minister David Cameron, who have both visited New Delhi in recent months.

While visiting India's tech hub Bangalore, Cameron caused a diplomatic spat with Pakistan when he said Islamabad could not 'look both ways' in promoting the export of terror while publicly working for stability in the region.

Pakistan's government says the country is a victim of terror as well and that it is doing all it can to combat extremism, including in the mountainous tribal border areas where its army has struggled to exert control.

Mr Sarkozy's visit to Mumbai — which later includes an address to business leaders at an Indo-French industry forum - wraps up a trade-focused visit heavily weighted on nuclear and defence deals.

Mr Sarkozy and India's Prime Minister Manmohan Singh on Monday unveiled plans for a 9.3-billion-dollar deal for France's Areva nuclear group to provide two reactors for a new plant in Maharashtra state, of which Mumbai is the capital.

The deal is short of a final sale contract but makes Areva a front-runner in the highly competitive race to sell nuclear technology to India, which wants atomic energy to supply a quarter of its electricity demands by 2050.

The United States and Japan are looking to increase civil nuclear cooperation, while Russia is already building two nuclear power plants in the southern state of Tamil Nadu.

Sarkozy's office has said that deals totalling 15 billion euros (20 billion dollars) have been or are about to be signed with Indian companies. They include a leasing agreement for 14 Airbus planes and the modernisation of 51 French-made Mirage fighter jets.