*

Anger rising over disputed election result

*

At least 18 killed in protests since October

*

Observers said election was not free and fair

*

Ruling Frelimo party in power since 1975

(Adds quotes from protesters in paragraphs 6 and 14, gas

projects in paragraph 13)

MAPUTO, Nov 7 (Reuters) - Mozambican police fired tear

gas at thousands of protesters in the capital Maputo on Thursday

during the biggest demonstration yet against the long-ruling

Frelimo party, which was declared the winner of a disputed

election last month.

Anger has mounted since election authorities said Frelimo

had won the Oct. 9 vote, extending its 49-year rule. Human

rights groups say at least 18 people have been killed in the

police crackdown on protests since then.

The election was hotly contested, with many young people

supporting independent candidate Venancio Mondlane, who says the

vote was rigged and encouraged demonstrations.

Protesters chanted "Power to the people" and "Frelimo must

fall" and some blockaded streets with burning tyres and held

homemade signs supporting Mondlane.

"This is it. If we don't stand up now, nothing will change,"

said Julia Macamo, 55, a street vendor and mother of six who

was still shaken by the tear gas she inhaled while protesting in

the Maxaquene neighbourhood. "It's time to see the back of

Frelimo."

Adriano Nuvunga, director of Mozambique's Centre for

Democracy and Human Rights, said the country had never seen such

large demonstrations.

Civil society groups and Western observers also said the

election was unfair and that results were altered. A Frelimo

spokesperson did not respond to requests for comment.

The party has been accused of vote-rigging in previous polls

and has denied it. This sparked smaller protests last year.

President Filipe Nyusi has not spoken since the protests

escalated. His defence minister has threatened to deploy the

army and warned against attempts to grab power.

DISPUTED VOTE COUNT

Mozambique's Constitutional Council has not yet certified

the election results, a process that usually takes around two

months.

On Tuesday it ordered the electoral commission to clarify

within 72 hours why there had been discrepancies in the number

of votes counted in the presidential, legislative and provincial

elections, according to a letter seen by Reuters.

An electoral commission spokesperson did not immediately

respond to a request for comment.

Many Mozambicans have expressed frustration at lack of

economic opportunities while the country is rich in natural

resources. TotalEnergies and Exxon Mobil ( XOM ) are

both developing billion-dollar gas projects in its far north

that have been halted by an Islamist insurgency.

"Our generation must act now to ensure a brighter future for

the next," said Jessica Muando, 22, a social activist and

student. "We are determined to face the risks."

South Africa has closed its main border crossing for

security reasons, and its foreign ministry advised its citizens

against all but essential travel to Mozambique.

South African logistics company Grindrod on

Thursday said it had suspended port and terminal operations in

Mozambique.