Italy's lower house of parliament has ratified a landmark treaty aimed at combating violence against women.

The new government vowed to prioritise the issue as thousands gathered in a southern town for the funeral of a 16-year-old girl allegedly killed by her boyfriend.

At the end of an impassioned parliamentary debate in Rome, MPs in the chamber of deputies voted unanimously to make Italy the fifth country to ratify the Council of Europe's wide-ranging convention on violence against women – a move activists said would be a key step towards improving society's response to the problem.

The vote was given an additional sense of urgency by events unfolding in the Calabrian town of Corigliano Calabro, where people gathered to pay their respects to Fabiana Luzzi, a teenager whose death has appalled a country becoming increasingly concerned by the rate of femicides, the gender-based killings of women.

Fabiana, a dance-mad schoolgirl, was allegedly stabbed repeatedly last week by her 17-year-old boyfriend. She is thought to have been still alive when he allegedly returned later to douse her in petrol and set her alight.

On a visit to Corigliano, the new equal opportunities minister, Josefa Idem, said the ratification of the so-called Istanbul convention was a good starting point for concrete political actions to help the fight against gender-based violence.

"Faced with Fabiana's death, I reaffirm the commitment of all the government and my ministry to make the fight against gender-based violence a key point of this legislature," she said, according to the Ansa news agency.

"I feel the need to ask forgiveness from her and from all women killed by the hand of those who abuse the word love. The state must be more effective in its commitment [and] be even closer to the victims."

There are no official statistics, partly because the definition remains disputed, but according to the women's organisation Casa delle Donne , 51 gender based murders of women have been documented in Italy so far this year. The group believes the real figure could be as much as a third higher.

Last week, as well as Fabiana's killing, a 35-year-old Romanian woman, Angelica Timis, was allegedly stabbed to death by her former partner in a small northern town near Milan. In Padua, a 50-year-old woman called Silvana Cassol was shot by her husband, who then turned the gun on himself.

Italy's national statistics agency, Istat, said in late 2011 that about one in three women were the victims of domestic violence.

After a visit to the country last year, the UN's special rapporteur on violence against women said there was an urgent need to tackle the problem.

Rashida Manjoo said: "Most manifestations of violence are under-reported in the context of a family-oriented and patriarchal society where domestic violence is not always perceived as a crime, there is economic dependency, and there are perceptions that the state response to such complaints will not be appropriate or helpful."

Before Italy officially ratifies the Istanbul convention, the vote in the chamber of deputies needs to be repeated in the upper house of parliament, or senate. In the current climate, ratification appears to be certain.

Angela Romanin, of Casa delle Donne, said the vote was an important step forward for Italy, but the government now needed to prove its mettle by following through on all the measures contained in the convention. "In Italy, the state is lacking. It hasn't done an awful lot to stop violence against women," she said.

Signed by more than 25 countries but so far ratified only by Albania, Turkey, Portugal and Montenegro, the convention needs the ratification of 10 – including eight Council of Europe member states – to come into effect.

Britain, although not among the initial signatories in 2011, followed suit last year, with David Cameron describing it as a "landmark agreement between countries that together we're going to drag this problem into broad daylight and tackle it head on".