The SNP has built upon its sweeping gains at the May general election with confident victories in council by-elections sparked by the resignation as councillors of the party's newly-elected MPs.

The party held Aberdeen City Council seats vacated by Kirsty Blackman, now MP for Aberdeen North, and Callum McCaig, now MP for Aberdeen South.

The by-elections repeated the large swings to the Scottish Nationalists seen at the general election.

The swing from Labour to the SNP in first-count votes was 19.8% in Ms Blackman's former ward of Hilton/Woodside/Stockethill and 22.9% in Mr McCaig's former ward of Kincorth/Nigg/Cove.

A similar swing of 25.3% from Labour to the Scottish Nationalists in first-count votes was recorded when the SNP held a seat in a by-election on July 9 at North Lanarkshire Council unrelated to the election of any new MP.

Thirteen new SNP MPs so far have stepped down as councillors to focus on their Westminster roles, prompting local polls.

Next Thursday will see a flurry of four Glasgow City Council by-elections, two of which follow the resignation as councillors of new SNP MPs - Martin Docherty (Dunbartonshire West) and Alison Thewliss (Glasgow Central). The other two by-elections follow the resignations of SNP and Green councillors.

A council by-election also takes place at South Lanarkshire where new SNP MP Angela Crawley (Lanark & Hamilton East) has stepped down as a councillor.

Other pending council by-elections in such circumstances are:

August 13: Falkirk, where John McNally is now SNP MP for Falkirk; and North Lanarkshire, where Marion Fellows is now SNP MP for Motherwell & Wishaw;

August 27: East Ayrshire - Alan Brown (Kilmarnock & Loudoun);

September 10: Edinburgh City - Deidre Brock (Edinburgh North & Leith); and Midlothian - Owen Thompson (Midlothian);

September 17: South Ayrshire - Corri Wilson (Ayr, Carrick & Cumnock);

Dates still to be set: Fife - Peter Grant (Glenrothes); and Highland - Drew Hendry (Inverness, Nairn, Badenoch & Strathspey).

Other SNP MPs who currently are councillors (excluding community councillors) are believed to include: Douglas Chapman (Dunfermline and Fife West); Martyn Day (Linlithgow & Falkirk East); and Steven Paterson (Stirling).

First-preference voting in the Hilton/Woodside/Stockethill contest was: SNP 1,690, Lab 771, C 350, Green 130, LD 125; and in Kincorth/Nigg/Cove: SNP 1,939, Lab 606, C 313, LD 207, Green 114.

SNP business convener Derek Mackay said: "This is an outstanding double success for the SNP in Aberdeen - and is a vote of confidence in the strong start that the new SNP MPs have made in standing up for Scotland's interests at Westminster."

He added: "It is clear that the SNP is in a very strong position as we approach next year's Scottish Parliament election - and seek to build on our outstanding record of delivery and success in government."