Victories in the upcoming by-elections will prove that the people are behind Prime Minister Najib Abdul Razak, according to Tourism and Culture Minister Nazri Abdul Aziz.

Therefore, he reminded Umno that since the contests would have a direct impact on Najib, caution must be exercised.

"This is not the time for us to conduct trials.

"Whatever the results (of the by-elections), they will have an impact on the prime minister. So we must be careful," the Umno supreme council member told reporters in Kuala Lumpur.

The Sungai Besar and Kuala Kangsar by-elections would be held simultaneously on June 18.

The contests are expected to serve as a litmus test for Najib (photo) with regard to the allegations and issues surrounding him, which he has blamed on those conspiring to topple him from power.

Last week, BN scored a thumping victory in the Sarawak state election, but the results were attributed to Chief Minister Adenan Satem, rather than the prime minister.

The two parliamentary seats were won with slim majorities in the last general election, with Sungai Besar in Selangor clinched by Umno with a 399-vote majority, whereas Kuala Kangsar in Perak was won with a margin of 1,082 votes.

The two seats fell vacant with the deaths of Plantation Industries and Commodities Deputy Minister Noriah Kasnon and Wan Muhammad Khairil Anuar Wan Ahmad in a helicopter crash in Sarawak on May 5.

Meanwhile, Nazri said to ensure victories in the by-elections, the choice of candidates is crucial and BN should prioritise local candidates.

"This is not the time for us to put an outsider as a candidate.

"Umno is very influential in rural areas particularly among Malays who prefer someone they know.

"BN candidates who contested in the last general election - from MPs to state assemblypersons - all of them were locals in their own constituencies," he added.

Nazri said while the party president, deputy president and secretary-general have the final word on this matter, local grassroots sentiments must not be ignored.

"We need to ensure that we can win with a bigger majority than before, particularly after our success in Sarawak," he added.